H3c Msr 2600 series User manual

H3C MSR Series Routers

Layer 3 - IP Services Configuration Guide(V7)

Hangzhou H3C Technologies Co., Ltd.

http://www.h3c.com

Software version: MSR-CMW710-R0007

Document version: 6W100-20140320

No part of this manual may be reproduced or transmitted in any form or by any means without prior

written consent of Hangzhou H3C Technologies Co., Ltd.

Trademarks

H3C, , H3CS, H3CIE, H3CNE, Aolynk, , H3Care, , IRF, NetPilot, Netflow,

SecEngine, SecPath, SecCenter, SecBlade, Comware, ITCMM and HUASAN are trademarks of

Hangzhou H3C Technologies Co., Ltd.

All other trademarks that may be mentioned in this manual are the property of their respective owners

Notice

The information in this document is subject to change without notice. Every effort has been made in the

preparation of this document to ensure accuracy of the contents, but all statements, information, and

recommendations in this document do not constitute the warranty of any kind, express or implied.

Preface

The H3C MSR documentation set includes 14 configuration guides, which describe the software features

for the H3C MSR Series Routers and guide you through the software configuration procedures. These

configuration guides also provide configuration examples to help you apply software features to different

network scenarios.

The Layer 3 - IP Services Configuration Guide(V7) describes IPv4/IPv6 fundamentals and configuration,

such as IP addressing, ARP, DNS, DHCP, NAT, GRE, and tunneling configuration.

This preface includes:

•Audience

•Conventions

•About the H3C MSR documentation set

•Obtaining documentation

•Technical support

•Documentation feedback

These configuration guides apply to the following models of the H3C MSR series routers:

Model

MSR 2600 •MSR 26-30

MSR 3600

•MSR 36-10

•MSR 36-20

•MSR 36-40

•MSR 36-60

•MSR3600-28

•MSR3600-51

MSR 5600

•MSR 56-60

•MSR 56-80

Audience

This documentation is intended for:

•Network planners

•Field technical support and servicing engineers

•Network administrators working with the routers

Conventions

This section describes the conventions used in this documentation set.

Command conventions

Convention Descri

p

tion

Boldface Bold text represents commands and keywords that you enter literally as shown.

Italic Italic text represents arguments that you replace with actual values.

[ ] Square brackets enclose syntax choices (keywords or arguments) that are optional.

{ x | y | ... }

Braces enclose a set of required syntax choices separated by vertical bars, from which

you select one.

[ x | y | ... ]

Square brackets enclose a set of optional syntax choices separated by vertical bars, from

which you select one or none.

{ x | y | ... } *

Asterisk marked braces enclose a set of required syntax choices separated by vertical

bars, from which you select at least one.

[ x | y | ... ] *

Asterisk marked square brackets enclose optional syntax choices separated by vertical

bars, from which you select one choice, multiple choices, or none.

&<1-n> The argument or keyword and argument combination before the ampersand (&) sign can

be entered 1 to n times.

# A line that starts with a pound (#) sign is comments.

Symbols

Convention Descri

p

tion

WARNING An alert that calls attention to important information that if not understood or followed can

result in personal injury.

CAUTION An alert that calls attention to important information that if not understood or followed can

result in data loss, data corruption, or damage to hardware or software.

IMPORTANT An alert that calls attention to essential information.

NOTE An alert that contains additional or supplementary information.

TIP An alert that provides helpful information.

Network topology icons

Represents a generic network device, such as a router, switch, or firewall.

Represents a routing-capable device, such as a router or Layer 3 switch.

Represents a generic switch, such as a Layer 2 or Layer 3 switch, or a router that supports

Layer 2 forwarding and other Layer 2 features.

Port numbering in examples

The port numbers in this document are for illustration only and might be unavailable on your device.

About the H3C MSR documentation set

The H3C MSR documentation set includes:

Cate

g

or

y

Documents

Pur

p

oses

Product description and

specifications Marketing brochures Describe product specifications and benefits.

Hardware specifications

and installation

Installation guide Provides a complete guide to hardware installation

and hardware specifications.

MSR Series Routers

Interface Module Manual

Provide the hardware specifications of cards.

Software configuration

MSR Series Routers

Configuration guides(v7)

Describe software features and configuration

procedures.

MSR Series Routers

Command references(v7)

Provide a quick reference to all available

commands.

Operations and

maintenance Release notes

Provide information about the product release,

including the version history, hardware and software

compatibility matrix, version upgrade information,

technical support information, and software

upgrading.

Obtaining documentation

You can access the most up-to-date H3C product documentation on the World Wide Web

at http://www.h3c.com.

Click the links on the top navigation bar to obtain different categories of product documentation:

[Technical Support & Documents > Technical Documents]—Provides hardware installation, software

upgrading, and software feature configuration and maintenance documentation.

[Products & Solutions]—Provides information about products and technologies, as well as solutions.

[Technical Support & Documents > Software Download]—Provides the documentation released with the

software version.

Technical support

servic[email protected]

http://www.h3c.com

Documentation feedback

You can e-mail your comments about product documentation to info@h3c.com.

We appreciate your comments.

i

Contents

Configuring ARP··························································································································································· 1

Overview············································································································································································1

ARP message format ················································································································································1

ARP operating mechanism ······································································································································1

ARP table···································································································································································2

Configuring a static ARP entry·········································································································································3

Setting the maximum number of dynamic ARP entries for a device ············································································4

Setting the maximum number of dynamic ARP entries for an interface ······································································4

Setting the aging timer for dynamic ARP entries ···········································································································5

Enabling dynamic ARP entry check ································································································································5

Enabling ARP log output···················································································································································5

Displaying and maintaining ARP·····································································································································6

Static ARP configuration example ···································································································································6

Network requirements··············································································································································6

Configuration procedure ·········································································································································7

Configuring gratuitous ARP ········································································································································· 8

Overview············································································································································································8

Gratuitous ARP packet learning······························································································································8

Periodic sending of gratuitous ARP packets ··········································································································8

Configuration procedure··················································································································································9

Enabling IP conflict notification ···································································································································· 10

Configuring proxy ARP··············································································································································11

Enabling common proxy ARP ······································································································································· 11

Enabling local proxy ARP·············································································································································· 11

Displaying proxy ARP···················································································································································· 12

Common proxy ARP configuration example··············································································································· 12

Network requirements··········································································································································· 12

Configuration procedure ······································································································································ 12

Configuring ARP snooping········································································································································14

Configuration procedure··············································································································································· 14

Displaying and maintaining ARP snooping ················································································································ 14

Configuring ARP fast-reply·········································································································································16

Overview········································································································································································· 16

Function ·································································································································································· 16

Operation······························································································································································· 16

Configuration procedure··············································································································································· 16

ARP fast-reply configuration example ·························································································································· 17

Network requirements··········································································································································· 17

Configuration procedure ······································································································································ 17

Configuring IP addressing·········································································································································19

Overview········································································································································································· 19

IP address classes·················································································································································· 19

Special IP addresses ············································································································································· 20

Subnetting and masking ······································································································································· 20

Assigning an IP address to an interface ······················································································································ 21

Configuration guidelines ······································································································································ 21

ii

Configuration procedure ······································································································································ 21

Configuring IP unnumbered ·········································································································································· 21

Configuration guidelines ······································································································································ 22

Configuration prerequisites ·································································································································· 22

Configuration procedure ······································································································································ 22

Displaying and maintaining IP addressing ················································································································· 22

IP address configuration example ································································································································ 23

Network requirements··········································································································································· 23

Configuration procedure ······································································································································ 23

Verifying the configuration··································································································································· 23

IP unnumbered configuration example ························································································································ 24

Network requirements··········································································································································· 24

Configuration procedure ······································································································································ 25

Verifying the configuration··································································································································· 25

DHCP overview ··························································································································································27

DHCP address allocation ·············································································································································· 27

Allocation mechanisms ········································································································································· 27

Dynamic IP address allocation process··············································································································· 28

IP address lease extension···································································································································· 28

DHCP message format··················································································································································· 29

DHCP options ································································································································································· 30

Common DHCP options········································································································································ 30

Custom DHCP options··········································································································································· 30

Protocols and standards ················································································································································ 32

Configuring the DHCP server····································································································································33

Overview········································································································································································· 33

DHCP address pool··············································································································································· 33

IP address allocation sequence···························································································································· 35

DHCP server configuration task list ······························································································································ 35

Configuring an address pool on the DHCP server····································································································· 35

Configuration task list ··········································································································································· 35

Creating a DHCP address pool··························································································································· 36

Specifying IP address ranges for a DHCP address pool ·················································································· 36

Specifying gateways for the client······················································································································· 39

Specifying a domain name suffix for the client·································································································· 40

Specifying DNS servers for the client·················································································································· 40

Specifying WINS servers and NetBIOS node type for the client····································································· 41

Specifying BIMS server information for the client ······························································································ 41

Specifying the TFTP server and boot file name for the client············································································ 42

Specifying a server for the DHCP client·············································································································· 42

Configuring Option 184 parameters for the client···························································································· 43

Configuring self-defined DHCP options ·············································································································· 43

Enabling DHCP ······························································································································································ 44

Enabling the DHCP server on an interface·················································································································· 44

Applying an address pool on an interface ················································································································· 45

Configuring IP address conflict detection···················································································································· 45

Enabling handling of Option 82·································································································································· 46

Configuring DHCP server compatibility······················································································································· 46

Configuring the DHCP server to broadcast all responses················································································· 46

Configure the DHCP server to ignore BOOTP requests ···················································································· 46

Configuring the DHCP server to send BOOTP responses in RFC 1048 format·············································· 47

Setting the DSCP value for DHCP packets sent by the DHCP server········································································ 47

Displaying and maintaining the DHCP server ············································································································ 48

iii

DHCP server configuration examples ·························································································································· 48

Static IP address assignment configuration example························································································· 48

Dynamic IP address assignment configuration example··················································································· 50

DHCP user class configuration example············································································································· 51

Self-defined DHCP option configuration example ····························································································· 52

Troubleshooting DHCP server configuration ··············································································································· 53

Symptom································································································································································· 53

Analysis ·································································································································································· 53

Solution··································································································································································· 53

Configuring the DHCP relay agent···························································································································55

Overview········································································································································································· 55

Operation······························································································································································· 55

DHCP relay agent support for Option 82 ·········································································································· 56

DHCP relay agent configuration task list····················································································································· 56

Enabling DHCP ······························································································································································ 57

Enabling the DHCP relay agent on an interface ········································································································ 57

Specifying DHCP servers on a relay agent················································································································· 57

Configuring the DHCP relay agent security functions ································································································ 58

Enabling the DHCP relay agent to record relay entries···················································································· 58

Enabling periodic refresh of dynamic relay entries··························································································· 58

Enabling DHCP starvation attack protection ······································································································ 59

Configuring the DHCP relay agent to release an IP address ···················································································· 60

Configuring Option 82 ················································································································································· 60

Setting the DSCP value for DHCP packets sent by the DHCP relay agent······························································· 61

Displaying and maintaining the DHCP relay agent ··································································································· 61

DHCP relay agent configuration examples················································································································· 61

DHCP relay agent configuration example·········································································································· 61

Option 82 configuration example······················································································································· 62

Troubleshooting DHCP relay agent configuration······································································································ 63

Symptom································································································································································· 63

Analysis ·································································································································································· 63

Solution··································································································································································· 63

Configuring the DHCP client ·····································································································································64

Enabling the DHCP client on an interface··················································································································· 64

Configuring a DHCP client ID for an interface ··········································································································· 64

Enabling duplicated address detection ······················································································································· 65

Setting the DSCP value for DHCP packets sent by the DHCP client ········································································· 65

Displaying and maintaining the DHCP client·············································································································· 66

DHCP client configuration example ····························································································································· 66

Network requirements··········································································································································· 66

Configuration procedure ······································································································································ 67

Verifying the configuration··································································································································· 67

Configuring DHCP snooping·····································································································································69

Overview········································································································································································· 69

Application of trusted and untrusted ports·········································································································· 69

DHCP snooping support for Option 82·············································································································· 70

DHCP snooping configuration task list ························································································································ 71

Configuring basic DHCP snooping······························································································································ 71

Configuring Option 82 ················································································································································· 72

Saving DHCP snooping entries ···································································································································· 73

Enabling DHCP starvation attack protection ··············································································································· 74

Enabling DHCP-REQUEST attack protection ··············································································································· 74

Configuring DHCP packet rate limit····························································································································· 75

iv

Displaying and maintaining DHCP snooping ············································································································· 75

DHCP snooping configuration examples····················································································································· 76

Basic DHCP snooping configuration example ··································································································· 76

Option 82 configuration example······················································································································· 77

Configuring the BOOTP client···································································································································79

BOOTP application························································································································································ 79

Obtaining an IP address dynamically ························································································································· 79

Protocols and standards ················································································································································ 79

Configuring an interface to use BOOTP for IP address acquisition·········································································· 80

Displaying and maintaining BOOTP client ················································································································· 80

BOOTP client configuration example ·························································································································· 80

Network requirements··········································································································································· 80

Configuration procedure ······································································································································ 80

Configuring DNS ·······················································································································································81

Overview········································································································································································· 81

Static domain name resolution····························································································································· 81

Dynamic domain name resolution······················································································································· 81

DNS proxy ····························································································································································· 82

DNS spoofing ························································································································································ 83

DNS configuration task list············································································································································ 84

Configuring the IPv4 DNS client ·································································································································· 85

Configuring static domain name resolution········································································································ 85

Configuring dynamic domain name resolution·································································································· 85

Configuring the IPv6 DNS client ·································································································································· 86

Configuring static domain name resolution········································································································ 86

Configuring dynamic domain name resolution·································································································· 87

Configuring the DNS proxy ·········································································································································· 87

Configuring DNS spoofing ··········································································································································· 88

Specifying the source interface for DNS packets ······································································································· 88

Configuring the DNS trusted interface························································································································· 89

Specifying the DSCP value for outgoing DNS packets······························································································ 90

Displaying and maintaining IPv4 DNS························································································································ 90

IPv4 DNS configuration examples ······························································································································· 90

Static domain name resolution configuration example ····················································································· 90

Dynamic domain name resolution configuration example ··············································································· 91

DNS proxy configuration example······················································································································ 94

IPv6 DNS configuration examples ······························································································································· 96

Static domain name resolution configuration example ····················································································· 96

Dynamic domain name resolution configuration example ··············································································· 96

DNS proxy configuration example····················································································································101

Troubleshooting IPv4 DNS configuration ··················································································································102

Symptom·······························································································································································102

Solution·································································································································································102

Troubleshooting IPv6 DNS configuration ··················································································································102

Symptom·······························································································································································102

Solution·································································································································································102

Configuring DDNS·················································································································································· 104

Overview·······································································································································································104

DDNS application ···············································································································································104

DDNS client configuration task list·····························································································································105

Configuring a DDNS policy········································································································································105

Configuration prerequisites ································································································································106

Configuration procedure ····································································································································106

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Applying the DDNS policy to an interface················································································································107

Specifying the DSCP value for outgoing DDNS packets ·························································································107

Displaying DDNS·························································································································································108

DDNS configuration examples ···································································································································108

DDNS configuration example with www.3322.org ·······················································································108

DDNS configuration example with PeanutHull server·····················································································109

Configuring NAT····················································································································································· 111

Terminology ··································································································································································111

NAT device ··························································································································································111

NAT interface ······················································································································································111

NAT address························································································································································112

NAT entry·····························································································································································112

NAT types ·····································································································································································112

Traditional NAT···················································································································································112

Bidirectional NAT················································································································································112

Twice NAT ···························································································································································112

Easy IP ··································································································································································112

NAT translation control ···············································································································································112

NAT features·································································································································································113

Static NAT····························································································································································113

Dynamic NAT ······················································································································································113

NAT Server ··························································································································································114

NAT hairpin ·························································································································································115

NAT entries···································································································································································116

NAT session entry················································································································································116

EIM entry ······························································································································································116

NO-PAT entry·······················································································································································116

Using NAT with other features····································································································································116

NAT with MPLS VPNs ·········································································································································116

NAT with DNS mapping ····································································································································117

NAT with ALG ·····················································································································································117

NAT configuration task list··········································································································································118

Configuring static NAT················································································································································118

Configuration prerequisites ································································································································118

Configuring outbound one-to-one static NAT···································································································118

Configuring outbound net-to-net static NAT ·····································································································119

Configuring inbound one-to-one static NAT ·····································································································120

Configuring inbound net-to-net static NAT········································································································120

Configuring dynamic NAT··········································································································································121

Configuration restrictions and guidelines ·········································································································121

Configuration prerequisites ································································································································121

Configuring outbound dynamic NAT················································································································121

Configuring inbound dynamic NAT··················································································································122

Configuring NAT Server··············································································································································123

Configuring common NAT Server ·····················································································································123

Configuring load sharing NAT Server ··············································································································124

Configuring NAT with DNS mapping ·······················································································································125

Configuring NAT hairpin ············································································································································125

Configuring NAT with ALG·········································································································································125

Configuring NAT logging ···········································································································································126

Displaying and maintaining NAT·······························································································································126

NAT configuration examples ······································································································································127

One-to-one static NAT for internal-to-external access······················································································127

Outbound dynamic NAT for internal-to-external access (non-overlapping addresses)································129

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Bidirectional NAT for internal-to-external access ·····························································································131

NAT Server for external-to-internal access········································································································133

NAT Server for external-to-internal access through domain name·································································136

Bidirectional NAT for external-to-internal access through NAT Server··························································138

NAT hairpin in C/S mode ·································································································································141

NAT hairpin in P2P mode for access between internal users·········································································144

Twice NAT for access between two VPNs with overlapping addresses ·······················································146

Load sharing NAT Server configuration example ···························································································148

NAT with DNS mapping configuration example·····························································································150

Basic IP forwarding on the device ························································································································· 154

FIB table ········································································································································································154

Displaying FIB table entries·········································································································································154

Configuring fast forwarding··································································································································· 156

Overview·······································································································································································156

Configuration procedure·············································································································································156

Displaying and maintaining fast forwarding ············································································································156

Fast forwarding configuration example·····················································································································157

Network requirements·········································································································································157

Configuration procedure ····································································································································157

Verifying the configuration·································································································································158

Displaying the adjacency table ····························································································································· 159

Optimizing IP performance ···································································································································· 161

Enabling an interface to receive and forward directed broadcasts destined for the directly connected network

·······················································································································································································161

Configuration procedure ····································································································································161

Configuration example ·······································································································································162

Configuring MTU for an interface ······························································································································162

Configuring TCP MSS for an interface ······················································································································163

Configuring TCP path MTU discovery ·······················································································································163

Enabling TCP SYN Cookie··········································································································································164

Configuring the TCP buffer size··································································································································165

Configuring TCP timers················································································································································165

Enabling sending ICMP error packets ·······················································································································165

Configuring rate limit for ICMP error messages ·······································································································167

Specifying the source address for ICMP packets ·····································································································167

Configuring IP virtual fragment reassembly ··············································································································168

Configuration guidelines ····································································································································168

Configuration procedure ····································································································································168

Configuration example ·······································································································································168

Displaying and maintaining IP performance optimization ······················································································169

Configuring UDP helper·········································································································································· 171

Overview·······································································································································································171

Configuration guidelines ·············································································································································171

Configuration procedure·············································································································································171

Displaying and maintaining UDP helper ···················································································································172

UDP helper configuration example ····························································································································172

Network requirements·········································································································································172

Configuration procedure ····································································································································172

Verifying the configuration·································································································································173

Configuring basic IPv6 settings······························································································································ 174

Overview·······································································································································································174

vii

IPv6 features·························································································································································174

IPv6 addresses·····················································································································································175

IPv6 ND protocol·················································································································································178

IPv6 path MTU discovery····································································································································180

IPv6 transition technologies·········································································································································180

Dual stack·····························································································································································180

Tunneling······························································································································································181

NAT-PT··································································································································································181

6PE········································································································································································181

Protocols and standards ··············································································································································181

IPv6 basics configuration task list·······························································································································182

Assigning IPv6 addresses to interfaces······················································································································183

Configuring an IPv6 global unicast address ····································································································183

Configuring an IPv6 link-local address ·············································································································185

Configuring an IPv6 anycast address ···············································································································186

Configuring IPv6 ND ···················································································································································186

Configuring a static neighbor entry ··················································································································186

Setting the maximum number of dynamic neighbor entries············································································187

Setting the aging timer for ND entries in stale state························································································187

Minimizing link-local ND entries························································································································188

Setting the hop limit ············································································································································188

Configuring parameters for RA messages········································································································188

Configuring the maximum number of attempts to send an NS message for DAD·······································191

Enabling ND proxy ·············································································································································191

Configuring path MTU discovery ·······························································································································193

Configuring the interface MTU ··························································································································193

Configuring a static path MTU for a specific IPv6 address ············································································193

Configuring the aging time for dynamic path MTUs·······················································································193

Controlling sending ICMPv6 packets·························································································································194

Configuring the rate limit for ICMPv6 error messages····················································································194

Enabling replying to multicast echo requests ···································································································194

Enabling sending ICMPv6 destination unreachable messages······································································194

Enabling sending ICMPv6 time exceeded messages······················································································195

Enabling sending ICMPv6 redirect messages ··································································································195

Specifying the source address for ICMPv6 packets ·································································································196

Displaying and maintaining IPv6 basics ···················································································································196

IPv6 basics configuration example ····························································································································198

Network requirements·········································································································································198

Configuration procedure ····································································································································199

Verifying the configuration·································································································································199

Troubleshooting IPv6 basics configuration················································································································203

Symptom·······························································································································································203

Solution·································································································································································203

DHCPv6 overview··················································································································································· 204

DHCPv6 address/prefix assignment··························································································································204

Rapid assignment involving two messages·······································································································204

Assignment involving four messages·················································································································204

Address/prefix lease renewal ····································································································································205

Stateless DHCPv6·························································································································································206

Protocols and standards ··············································································································································206

Configuring the DHCPv6 server····························································································································· 207

Overview·······································································································································································207

IPv6 address assignment ····································································································································207

viii

IPv6 prefix assignment········································································································································207

Concepts·······························································································································································208

DHCPv6 address pool ········································································································································209

IPv6 address/prefix allocation sequence ·········································································································210

Configuration task list ··················································································································································210

Configuring IPv6 prefix assignment ···························································································································210

Configuration guidelines ····································································································································211

Configuration procedure ····································································································································211

Configuring IPv6 address assignment························································································································212

Configuration guidelines ····································································································································212

Configuration procedure ····································································································································212

Configuring network parameters assignment ···········································································································213

Configuring the DHCPv6 server on an interface ······································································································214

Configuration guidelines ····································································································································214

Configuration procedure ····································································································································214

Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 server ·····························································215

Displaying and maintaining the DHCPv6 server ······································································································215

DHCPv6 server configuration examples····················································································································216

Dynamic IPv6 prefix assignment configuration example ················································································216

Dynamic IPv6 address assignment configuration example·············································································218

Configuring the DHCPv6 relay agent···················································································································· 221

Configuration guidelines ·············································································································································222

Configuration procedure·············································································································································222

Displaying and maintaining the DHCPv6 relay agent·····························································································223

DHCPv6 relay agent configuration example ············································································································223

Network requirements·········································································································································223

Configuration procedure ····································································································································223

Verifying the configuration·································································································································224

Configuring DHCPv6 snooping ····························································································································· 225

Overview·······································································································································································225

Application of trusted and untrusted ports········································································································225

H3C implementation of Option 18 and Option 37·································································································226

Option 18 for DHCPv6 snooping······················································································································226

DHCPv6 snooping support for Option 37········································································································227

DHCPv6 snooping configuration task list ··················································································································227

Configuring basic DHCPv6 snooping························································································································228

Configuring Option 18 and Option 37 ····················································································································228

Saving DHCPv6 snooping entries ······························································································································229

Setting the maximum number of DHCPv6 snooping entries····················································································230

Enabling DHCPv6-REQUEST check····························································································································230

Displaying and maintaining DHCPv6 snooping·······································································································231

DHCPv6 snooping configuration example················································································································231

Network requirements·········································································································································231

Configuration procedure ····································································································································232

Verifying the configuration·································································································································232

Configuring IPv6 fast forwarding··························································································································· 233

Overview·······································································································································································233

Configuration procedure·············································································································································233

Displaying and maintaining IPv6 fast forwarding ····································································································233

IPv6 fast forwarding configuration example ·············································································································234

Network requirements·········································································································································234

Configuration procedure ····································································································································234

Verifying the configuration·································································································································234

ix

Configuring tunneling ············································································································································· 236

Overview·······································································································································································236

IPv6 over IPv4 tunneling ·····································································································································236

IPv4 over IPv4 tunneling ·····································································································································239

IPv4 over IPv6 tunneling ·····································································································································240

IPv6 over IPv6 tunneling ·····································································································································243

Protocols and standards ·····································································································································243

Tunneling configuration task list ·································································································································244

Configuring a tunnel interface····································································································································244

Configuring an IPv6 over IPv4 manual tunnel···········································································································245

Configuration example ·······································································································································246

Configuring an automatic IPv4-compatible IPv6 tunnel ···························································································248

Configuration example ·······································································································································249

Configuring a 6to4 tunnel···········································································································································250

6to4 tunnel configuration example ···················································································································251

6to4 relay configuration example ·····················································································································253

Configuring an ISATAP tunnel ····································································································································254

Configuration example ·······································································································································255

Configuring an IPv4 over IPv4 tunnel ························································································································258

Configuration example ·······································································································································259

Configuring an IPv4 over IPv6 manual tunnel···········································································································260

Configuration example ·······································································································································261

Configuring a DS-Lite tunnel ·······································································································································263

Configuration example ·······································································································································264

Configuring an IPv6 over IPv6 tunnel ························································································································266

Configuration example ·······································································································································267

Displaying and maintaining tunneling configuration ·······························································································269

Troubleshooting tunneling configuration ···················································································································269

Symptom·······························································································································································269

Analysis ································································································································································269

Solution·································································································································································269

Configuring flow classification······························································································································· 270

Specifying a flow classification policy·······················································································································270

Index ········································································································································································ 271

1

Configuring ARP

This chapter describes how to configure the Address Resolution Protocol (ARP).

Overview

ARP resolves IP addresses into MAC addresses on Ethernet networks.

ARP message format

ARP uses two types of messages: ARP request and ARP reply. Figure 1 shows the format of ARP

request/reply messages. Numbers in the figure refer to field lengths.

Figure 1 ARP message format

•Hardware type—Hardware address type. The value 1 represents Ethernet.

•Protocol type—Type of the protocol address to be mapped. The hexadecimal value 0x0800

represents IP.

•Hardware address length and protocol address length—Length, in bytes, of a hardware address

and a protocol address. For an Ethernet address, the value of the hardware address length field is

6. For an IPv4 address, the value of the protocol address length field is 4.

•OP—Operation code, which describes the type of ARP message. Value 1 represents an ARP request,

and value 2 represents an ARP reply.

•Sender hardware address—Hardware address of the device sending the message.

•Sender protocol address—Protocol address of the device sending the message.

•Target hardware address—Hardware address of the device to which the message is being sent.

•Target protocol address—Protocol address of the device to which the message is being sent.

ARP operating mechanism

As shown in Figure 2, Host A and Host B are on the same subnet. Host A sends a packet to Host B as

follows:

1. Host A looks through the ARP table for an ARP entry for Host B. If one entry is found, Host A uses

the MAC address in the entry to encapsulate the IP packet into a data link layer frame. Then Host

A sends the frame to Host B.

2

2. If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an ARP request. The

payload of the ARP request comprises the following information:

{Sender IP address and sender MAC address—Host A's IP address and MAC address.

{Target IP address—Host B's IP address.

{Target MAC address—An all-zero MAC address.

All hosts on this subnet can receive the broadcast request, but only the requested host (Host B)

processes the request.

3. Host B compares its own IP address with the target IP address in the ARP request. If they are the

same, Host B:

a. Adds the sender IP address and sender MAC address into its ARP table.

b. Encapsulates its MAC address into an ARP reply.

c. Unicasts the ARP reply to Host A.

4. After receiving the ARP reply, Host A:

a. Adds the MAC address of Host B into its ARP table.

b. Encapsulates the MAC address into the packet and sends the packet to Host B.

Figure 2 ARP address resolution process

If Host A and Host B are on different subnets, Host A sends a packet to Host B as follows:

5. Host A broadcasts an ARP request where the target IP address is the IP address of the gateway.

6. The gateway responds with its MAC address in an ARP reply to Host A.

7. Host A uses the gateway's MAC address to encapsulate the packet, and then sends the packet to

the gateway.

8. If the gateway has an ARP entry for Host B, it forwards the packet to Host B directly. If not, the

gateway broadcasts an ARP request, in which the target IP address is the IP address of Host B.

9. After the gateway gets the MAC address of Host B, it sends the packet to Host B.

ARP table

An ARP table stores dynamic and static ARP entries.

Dynamic ARP entry

ARP automatically creates and updates dynamic entries. A dynamic ARP entry is removed when its aging

timer expires or the output interface goes down. In addition, a dynamic ARP entry can be overwritten by

a static ARP entry.

3

Static ARP entry

A static ARP entry is manually configured and maintained. It does not age out and cannot be overwritten

by any dynamic ARP entry.

Static ARP entries protect communication between devices because attack packets cannot modify the

IP-to-MAC mapping in a static ARP entry.

Static ARP entries include long and short ARP entries.

•A long static ARP entry comprises the IP address, MAC address, VLAN, and output interface. It is

directly used for forwarding packets.

•A short static ARP entry comprises only the IP address and MAC address.

{If the output interface is a Layer 3 Ethernet interface, the short ARP entry can be directly used to

forward packets.

{If the output interface is a VLAN interface, the device first sends an ARP request whose target IP

address is the IP address of the short entry. If the sender IP and MAC addresses in the received

ARP reply match the IP and MAC addresses of the short static ARP entry, the device adds the

interface that received the ARP reply to the short static ARP entry, and uses the resolved short

static ARP entry to forward IP packets.

To communicate with a host by using a fixed IP-to-MAC mapping, configure a short static ARP entry on

the device. To communicate with a host by using a fixed IP-to-MAC mapping through a specific interface

in a specific VLAN, configure a long static ARP entry on the device.

Configuring a static ARP entry

A static ARP entry is effective when the device works correctly. If a VLAN or VLAN interface is deleted,

any long static ARP entry in the VLAN is deleted, and any resolved short static ARP entry in the VLAN

becomes unresolved.

A resolved short static ARP entry becomes unresolved upon certain events. For example, it becomes

unresolved when the resolved output interface goes down.

A long static ARP entry is ineffective if the IP address in the entry conflicts with a local IP address, or no

local interface has an IP address in the same subnet as the IP address in the ARP entry. An ineffective long

static ARP entry cannot be used to forward packets.

Follow these guidelines when you configure a static ARP entry:

•The vlan-id argument must be the ID of an existing VLAN where the ARP entry resides. The specified

Ethernet interface must belong to that VLAN. The VLAN interface of the VLAN must be created.

•The IP address of the VLAN interface of the VLAN specified by the vlan-id argument must belong to

the same subnet as the IP address specified by the ip-address argument.

To configure a static ARP entry:

Step Command Remarks

1. Enter system view. system-view N/A

4

Step Command Remarks

2. Configure a static ARP

entry.

•Configure a long static ARP entry:

arp static ip-address mac-address

vlan-id interface-type interface-number

[ vpn-instance vpn-instance-name ]

•Configure a short static ARP entry:

arp static ip-address mac-address

[ vpn-instance vpn-instance-name ]

Use either command.

By default, no static ARP entry is

configured.

Setting the maximum number of dynamic ARP

entries for a device

A device can dynamically learn ARP entries. To prevent a device from holding too many ARP entries, you

can set the maximum number of dynamic ARP entries that the device can learn. When the maximum

number is reached, the device stops learning ARP entries.

If you set a value lower than the number of existing dynamic ARP entries, the device does not remove the

existing entries unless they are aged out, and the device stops learning ARP entries until the number of

dynamic ARP entries is below the configured value.

To set the maximum number of dynamic ARP entries for a device:

Ste

p

Command

Remarks

1. Enter system view. system-view N/A

2. Set the maximum

number of dynamic

ARP entries for the

device.

arp max-learning-number

number

If the value for the number argument is set to

0, the device is disabled from learning

dynamic ARP entries.

Setting the maximum number of dynamic ARP

entries for an interface

An interface can dynamically learn ARP entries. To prevent an interface from holding too many ARP

entries, you can set the maximum number of dynamic ARP entries that the interface can learn. When the

maximum number is reached, the interface stops learning ARP entries.

The Layer-2 interface can learn an ARP entry only when both its maximum number and the VLAN

interface's maximum number are not reached.

To set the maximum number of dynamic ARP entries for an interface:

Step Command Remarks

3. Enter system view. system-view N/A

4. Enter interface view. interface interface-type

interface-number N/A

5

Step Command Remarks

5. Set the maximum number of

dynamic ARP entries for the

interface.

arp max-learning-num number

If the value of the number argument is set

to 0, the interface is disabled from

learning dynamic ARP entries.

Setting the aging timer for dynamic ARP entries

Each dynamic ARP entry in the ARP table has a limited lifetime, called an aging timer. The aging timer

of a dynamic ARP entry is reset each time the dynamic ARP entry is updated. A dynamic ARP entry that

is not updated before its aging timer expires is deleted from the ARP table.

To set the aging timer for dynamic ARP entries:

Step Command Remarks

1. Enter system view. system-view N/A

2. Set the aging timer for dynamic ARP

entries. arp timer aging aging-time By default, the aging time for

dynamic ARP entries is 20 minutes.

Enabling dynamic ARP entry check

The dynamic ARP entry check function controls whether the device supports dynamic ARP entries

containing multicast MAC addresses.

When dynamic ARP entry check is enabled, the device cannot learn dynamic ARP entries containing

multicast MAC addresses, and you cannot manually add static ARP entries containing multicast MAC

addresses.

When dynamic ARP entry check is disabled, the device can learn dynamic ARP entries containing

multicast MAC addresses obtained from the ARP packets sourced from a unicast MAC address. You can

also manually add static ARP entries containing multicast MAC addresses.

To enable dynamic ARP entry check:

Step Command Remarks

1. Enter system view. system-view N/A

2. Enable dynamic ARP entry check.

arp check enable By default, dynamic ARP entry check is

enabled.

Enabling ARP log output

This function enables a device to output ARP logs generated in ARP resolution.

To enable ARP log output:

H3C MSR 2600 Series User manual

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