HPE StoreOnce 3100 User manual
HPE 3100 48 v2 Switch
Layer 3—IP Services
Configuration Guide
Part number: 5998-7643R
Software version: Release 2111
Document version: 6W100-20160122
© Copyright 2016 Hewlett Packard Enterprise Development LP
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Contents
Configuring ARP··············································································1
Overview··································································································································1
ARP message format···········································································································1
ARP operation····················································································································1
ARP table··························································································································2
Configuring a static ARP entry······································································································3
Configuring the maximum number of dynamic ARP entries for an interface ············································3
Setting the aging timer for dynamic ARP entries ···············································································4
Enabling dynamic ARP entry check ·······························································································4
Configuring ARP quick update······································································································5
Configuring multicast ARP ···········································································································5
Displaying and maintaining ARP ···································································································6
ARP configuration examples ········································································································6
Static ARP entry configuration example····················································································6
Multicast ARP configuration example·······················································································7
Configuring gratuitous ARP······························································10
Overview································································································································10
Gratuitous ARP packet learning····························································································10
Periodic sending of gratuitous ARP packets············································································10
Configuration guidelines············································································································10
Configuration procedure············································································································11
Enabling IP conflict notification····································································································11
Configuring proxy ARP····································································12
Overview································································································································12
Common proxy ARP ··········································································································12
Local proxy ARP ···············································································································12
Enabling common proxy ARP·····································································································13
Enabling local proxy ARP ··········································································································13
Displaying and maintaining proxy ARP ·························································································13
Proxy ARP configuration examples······························································································14
Common proxy ARP configuration example ············································································14
Local proxy ARP configuration example in case of port isolation··················································15
Local proxy ARP configuration example in isolate-user-VLAN·····················································16
Configuring ARP snooping·······························································18
Overview································································································································18
Configuration procedure············································································································18
Displaying and maintaining ARP snooping ····················································································18
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 ························································································20
Configuration guidelines ·····································································································21
Configuration procedure ·····································································································21
Configuration example········································································································21
Configuring IP unnumbered········································································································23
Overview·························································································································23
Configuration guidelines ·····································································································23
Configuration prerequisites··································································································23
Configuration procedure ·····································································································23
Displaying and maintaining IP addressing ·····················································································24
i
DHCP overview ·············································································25
DHCP address allocation···········································································································25
Dynamic IP address allocation process··················································································25
IP address lease extension··································································································26
DHCP message format ·············································································································26
DHCP options ·························································································································27
Common DHCP options······································································································28
Custom options·················································································································28
Protocols and standards············································································································32
Configuring DHCP server·································································33
Overview································································································································33
DHCP address pool···········································································································33
IP address allocation sequence····························································································34
DHCP server configuration task list······························································································34
Configuring an address pool for the DHCP server···········································································35
Configuration task list·········································································································35
Creating a DHCP address pool ····························································································35
Configuring address allocation mode for a common address pool················································36
Configuring dynamic address allocation for an extended address pool··········································38
Configuring a domain name suffix for the client········································································38
Configuring DNS servers for the client ···················································································39
Configuring WINS servers and NetBIOS node type for the client ·················································39
Configuring BIMS server information for the client ····································································39
Configuring gateways for the client························································································40
Configuring Option 184 parameters for the client with voice service ·············································40
Configuring the TFTP server and bootfile name for the client ······················································41
Specifying a server's IP address for the DHCP client·································································41
Configuring self-defined DHCP options ··················································································42
Enabling DHCP ·······················································································································42
Enabling the DHCP server on an interface ····················································································43
Configuration guidelines ·····································································································43
Configuration procedure ·····································································································43
Applying an extended address pool on an interface·········································································43
Configuring the DHCP server security functions ·············································································44
Configuration prerequisites··································································································44
Enabling unauthorized DHCP server detection ········································································44
Configuring IP address conflict detection················································································44
Enabling client offline detection···································································································45
Enabling handling of Option 82 ···································································································45
Configuration prerequisites··································································································45
Enabling Option 82 handling································································································46
Specifying the threshold for sending trap messages ········································································46
Configuration prerequisites··································································································46
Configuration procedure ·····································································································46
Setting the DSCP value for DHCP packets····················································································46
Displaying and maintaining the DHCP server·················································································47
DHCP server configuration examples···························································································47
Static IP address assignment configuration example·································································48
Dynamic IP address assignment configuration example·····························································49
Self-defined option configuration example···············································································50
Troubleshooting DHCP server configuration ··················································································51
Symptom·························································································································51
Analysis ··························································································································51
Solution···························································································································51
Configuring DHCP relay agent ··························································53
Overview································································································································53
Fundamentals···················································································································53
DHCP relay agent support for Option 82·················································································54
DHCP relay agent configuration task list ·······················································································54
ii
Enabling DHCP ·······················································································································55
Enabling the DHCP relay agent on an interface··············································································55
Correlating a DHCP server group with a relay agent interface····························································55
Configuration guidelines ·····································································································55
Configuration procedure ·····································································································56
Configuring the DHCP relay agent security functions·······································································56
Configuring address check ··································································································56
Configuring periodic refresh of dynamic client entries································································57
Enabling unauthorized DHCP server detection ········································································57
Enabling DHCP starvation attack protection············································································58
Enabling offline detection···········································································································58
Configuring the DHCP relay agent to release an IP address······························································59
Configuring the DHCP relay agent to support Option 82···································································59
Configuration prerequisites··································································································59
Configuration guidelines ·····································································································59
Configuration procedure ·····································································································60
Setting the DSCP value for DHCP packets····················································································60
Displaying and maintaining the DHCP relay agent ··········································································61
DHCP relay agent configuration examples ····················································································61
DHCP relay agent configuration example ···············································································61
DHCP relay agent Option 82 support configuration example·······················································62
Troubleshooting DHCP relay agent configuration············································································63
Symptom·························································································································63
Analysis ··························································································································63
Solution···························································································································63
Configuring DHCP client··································································64
Configuration restrictions···········································································································64
Enabling the DHCP client on an interface······················································································64
Setting the DSCP value for DHCP packets····················································································64
Displaying and maintaining the DHCP client ··················································································65
DHCP client configuration example······························································································65
Network requirements ········································································································65
Configuration procedure ·····································································································65
Verifying the configuration···································································································66
Configuring DHCP snooping·····························································68
DHCP snooping functions··········································································································68
Ensuring that DHCP clients obtain IP addresses from authorized DHCP servers·····························68
Recording IP-to-MAC mappings of DHCP clients ·····································································68
Application environment of trusted ports ·······················································································69
Configuring a trusted port connected to a DHCP server·····························································69
Configuring trusted ports in a cascaded network·············································································69
DHCP snooping support for Option 82··························································································70
DHCP snooping configuration task list··························································································71
Configuring DHCP snooping basic functions··················································································71
Configuring DHCP snooping to support Option 82···········································································72
Configuring DHCP snooping entries backup ··················································································74
Enabling DHCP starvation attack protection···················································································75
Enabling DHCP-REQUEST message attack protection····································································75
Enabling MAC and port check·····································································································76
Configuring DHCP packet rate limit······························································································76
Displaying and maintaining DHCP snooping ··················································································76
DHCP snooping configuration examples·······················································································77
DHCP snooping configuration example··················································································77
DHCP snooping Option 82 support configuration example ·························································78
Configuring BOOTP client································································79
Overview································································································································79
BOOTP application············································································································79
Obtaining an IP address dynamically·····················································································79
Protocols and standards ·····································································································79
iii
Configuration restrictions···········································································································79
Configuring an interface to dynamically obtain an IP address through BOOTP ······································79
Displaying and maintaining BOOTP client configuration ···································································80
BOOTP client configuration example····························································································80
Network requirements ········································································································80
Configuration procedure ·····································································································80
Configuring IPv4 DNS·····································································81
Overview································································································································81
Static domain name resolution ·····························································································81
Dynamic domain name resolution ·························································································81
DNS proxy·······················································································································82
DNS spoofing···················································································································83
Configuring the IPv4 DNS client··································································································84
Configuring static domain name resolution··············································································84
Configuring dynamic domain name resolution··········································································84
Configuring the DNS proxy·········································································································85
Configuring DNS spoofing··········································································································85
Setting the DSCP value for DNS packets ······················································································86
Specifying the source interface for DNS packets·············································································86
Displaying and maintaining IPv4 DNS ··························································································86
Static domain name resolution configuration example······································································87
Network requirements ········································································································87
Configuration procedure ·····································································································87
Dynamic domain name resolution configuration example··································································88
Network requirements ········································································································88
Configuration procedure ·····································································································88
Verifying the configuration···································································································90
DNS proxy configuration example································································································91
Network requirements ········································································································91
Configuration procedure ·····································································································91
Verifying the configuration···································································································92
Troubleshooting IPv4 DNS configuration·······················································································92
Symptom·························································································································92
Solution···························································································································92
Basic IP forwarding on the device······················································93
FIB table ································································································································93
Displaying FIB table entries········································································································93
Configuring load sharing··································································95
Configuration procedure············································································································95
Load sharing configuration example·····························································································95
Network requirements ········································································································95
Configuration procedure ·····································································································95
Verifying the configuration···································································································97
Configuring IRDP···········································································98
Overview································································································································98
Background······················································································································98
Working mechanism ··········································································································98
Concepts·························································································································99
Protocols and standards ·····································································································99
Configuration procedure············································································································99
IRDP configuration example····································································································· 100
Network requirements ······································································································ 100
Configuration procedure ··································································································· 101
Verifying the configuration································································································· 101
Optimizing IP performance····························································· 102
Enabling receiving and forwarding of directed broadcasts to a directly connected network····················· 102
Enabling receiving of directed broadcasts to a directly connected network··································· 102
iv
Enabling forwarding of directed broadcasts to a directly connected network································· 102
Configuration example······································································································ 103
Configuring TCP attributes······································································································· 103
Configuring TCP path MTU discovery·················································································· 103
Configuring the TCP send/receive buffer size········································································ 104
Configuring TCP timers ···································································································· 104
Configuring ICMP to send error packets······················································································ 105
Advantages of sending ICMP error packets··········································································· 105
Disadvantages of sending ICMP error packets······································································· 106
Configuration procedure ··································································································· 106
Displaying and maintaining IP performance optimization ································································ 106
Configuring UDP helper································································· 108
Overview······························································································································ 108
Configuration restrictions and guidelines····················································································· 108
Configuration procedure·········································································································· 108
Displaying and maintaining UDP helper······················································································ 109
UDP helper configuration example····························································································· 109
Network requirements ······································································································ 109
Configuration procedure ··································································································· 109
Configuring IPv6 basics································································· 111
Overview······························································································································ 111
IPv6 features·················································································································· 111
IPv6 addresses··············································································································· 112
IPv6 neighbor discovery protocol ························································································ 114
IPv6 path MTU discovery ·································································································· 117
IPv6 transition technologies······························································································· 117
Protocols and standards ··································································································· 118
IPv6 basics configuration task list······························································································ 118
Configuring basic IPv6 functions ······························································································· 119
Enabling IPv6················································································································· 119
Configuring an IPv6 global unicast address··········································································· 119
Configuring an IPv6 link-local address ················································································· 121
Configure an IPv6 anycast address····················································································· 122
Configuring IPv6 ND··············································································································· 123
Configuring a static neighbor entry······················································································ 123
Configuring the maximum number of neighbors dynamically learned·········································· 123
Setting the age timer for ND entries in stale state··································································· 124
Configuring parameters related to RA messages···································································· 124
Configuring the maximum number of attempts to send an NS message for DAD··························· 126
Configuring ND snooping·································································································· 127
Enabling ND proxy··········································································································· 128
Configuring path MTU discovery ······························································································· 130
Configuring a static path MTU for a specific IPv6 address ························································ 130
Configuring the aging time for dynamic path MTUs································································· 130
Configuring IPv6 TCP properties······························································································· 131
Configuring ICMPv6 packet sending ·························································································· 131
Configuring the maximum ICMPv6 error packets sent in an interval············································ 131
Enabling replying to multicast echo requests········································································· 132
Enabling sending ICMPv6 time exceeded messages ······························································ 132
Enabling sending ICMPv6 destination unreachable messages·················································· 132
Enabling sending ICMPv6 redirect messages········································································ 133
Enabling a device to discard IPv6 packets that contain extension headers ········································· 133
Configuring multicast ND········································································································· 134
Displaying and maintaining IPv6 basics configuration ···································································· 134
IPv6 basics configuration example····························································································· 135
Network requirements ······································································································ 135
Configuration procedure ··································································································· 136
Verifying the configuration································································································· 137
Troubleshooting IPv6 basics configuration··················································································· 141
Symptom······················································································································· 141
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Solution························································································································· 141
DHCPv6 overview········································································ 142
Hardware compatibility············································································································ 142
Introduction to DHCPv6··········································································································· 142
DHCPv6 address/prefix assignment··························································································· 142
Rapid assignment involving two messages ··········································································· 142
Assignment involving four messages··················································································· 142
Address/prefix lease renewal···································································································· 143
Configuring stateless DHCPv6·································································································· 144
Operation ······················································································································ 144
Protocols and standards·········································································································· 145
Configuring DHCPv6 server ··························································· 146
Overview······························································································································ 146
Concepts······················································································································· 146
Prefix selection process···································································································· 147
DHCPv6 server configuration task list························································································· 147
Enabling the DHCPv6 server···································································································· 147
Creating a prefix pool·············································································································· 148
Configuring a DHCPv6 address pool·························································································· 148
Configuration restrictions and guidelines ·············································································· 148
Configuration procedure ··································································································· 148
Applying the address pool to an interface···················································································· 149
Setting the DSCP value for DHCPv6 packets··············································································· 150
Displaying and maintaining the DHCPv6 server············································································ 150
DHCPv6 server configuration example ······················································································· 150
Network requirements ······································································································ 150
Configuration considerations······························································································ 151
Configuration procedure ··································································································· 151
Verifying the configuration································································································· 152
Configuring DHCPv6 relay agent····················································· 154
Overview······························································································································ 154
DHCPv6 relay agent operation··························································································· 154
Configuring the DHCPv6 relay agent·························································································· 155
Configuration guidelines ··································································································· 155
Configuration procedure ··································································································· 155
Setting the DSCP value for DHCPv6 packets··············································································· 156
Displaying and maintaining the DHCPv6 relay agent ····································································· 156
DHCPv6 relay agent configuration example················································································· 156
Network requirements ······································································································ 156
Configuration procedure ··································································································· 157
Verifying the configuration································································································· 157
Configuring DHCPv6 client····························································· 159
Overview······························································································································ 159
Configuration guidelines·········································································································· 159
Configuring IPv6 address acquisition·························································································· 159
Configuring stateless DHCPv6·································································································· 159
Setting the DSCP value for DHCPv6 packets··············································································· 160
Displaying and maintaining the DHCPv6 client ············································································· 160
Stateless DHCPv6 configuration example ··················································································· 160
Network requirements ······································································································ 160
Configuration procedure ··································································································· 161
Verifying the configuration································································································· 161
Configuring DHCPv6 snooping························································ 163
Overview······························································································································ 163
Ensuring that DHCPv6 clients obtain IPv6 addresses from authorized DHCPv6 servers ················· 163
Recording IP-to-MAC mappings of DHCPv6 clients ································································ 164
Enabling DHCPv6 snooping····································································································· 164
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Configuring a DHCPv6 snooping trusted port··············································································· 164
Configuring the maximum number of DHCPv6 snooping entries an interface can learn························· 165
Configuring DHCPv6 snooping to support Option 18 and Option 37·················································· 165
Displaying and maintaining DHCPv6 snooping············································································· 166
DHCPv6 snooping configuration example ··················································································· 166
Network requirements ······································································································ 166
Configuration procedure ··································································································· 167
Verifying the configuration································································································· 167
Configuring IPv6 DNS··································································· 168
Overview······························································································································ 168
Configuring the IPv6 DNS client································································································ 168
Configuring static domain name resolution············································································ 168
Configuring dynamic domain name resolution········································································ 168
Setting the DSCP value for IPv6 DNS packets ············································································· 169
Displaying and maintaining IPv6 DNS ························································································ 169
Static domain name resolution configuration example···································································· 170
Network requirements ······································································································ 170
Configuration procedure ··································································································· 170
Dynamic domain name resolution configuration example································································ 171
Network requirements ······································································································ 171
Configuration procedure ··································································································· 171
Verifying the configuration································································································· 174
Configuring tunneling···································································· 176
Overview······························································································································ 176
IPv6 over IPv4 tunneling··································································································· 176
IPv4 over IPv4 tunneling··································································································· 178
IPv4 over IPv6 tunneling··································································································· 179
IPv6 over IPv6 tunneling··································································································· 180
Protocols and standards ··································································································· 180
Tunneling configuration task list ································································································ 181
Configuring a tunnel interface··································································································· 181
Configuration guidelines ··································································································· 181
Configuration procedure ··································································································· 181
Configuring an IPv6 manual tunnel ···························································································· 182
Configuration prerequisites································································································ 182
Configuration guidelines ··································································································· 182
Configuration procedure ··································································································· 183
Configuration example······································································································ 183
Configuring a 6to4 tunnel········································································································· 187
Configuration prerequisites································································································ 187
Configuration guidelines ··································································································· 187
Configuration procedure ··································································································· 187
Configuration example······································································································ 188
Configuring an ISATAP tunnel ·································································································· 190
Configuration prerequisites································································································ 190
Configuration guidelines ··································································································· 190
Configuration procedure ··································································································· 191
Configuration example······································································································ 192
Configuring an IPv4 over IPv4 tunnel ························································································· 194
Configuration prerequisites································································································ 194
Configuration guidelines ··································································································· 194
Configuration procedure ··································································································· 195
Configuration example······································································································ 195
Configuring an IPv4 over IPv6 tunnel ························································································· 198
Configuration prerequisites································································································ 198
Configuration guidelines ··································································································· 198
Configuration procedure ··································································································· 199
Configuration example······································································································ 199
Configuring an IPv6 over IPv6 tunnel ························································································· 203
Configuration prerequisites································································································ 203
vii
viii
Configuration guidelines ··································································································· 203
Configuration procedure ··································································································· 203
Configuration example······································································································ 204
Displaying and maintaining tunneling configuration ······································································· 207
Troubleshooting tunneling configuration······················································································ 208
Symptom······················································································································· 208
Solution························································································································· 208
Configuring GRE·········································································· 209
Overview······························································································································ 209
GRE encapsulation format ································································································ 209
GRE encapsulation and de-encapsulation processes······························································ 210
Protocols and standards ··································································································· 210
Configuring a GRE over IPv4 tunnel··························································································· 211
Configuration prerequisites································································································ 211
Configuration guidelines ··································································································· 211
Configuration procedure ··································································································· 211
Configuring a GRE over IPv6 tunnel··························································································· 212
Configuration prerequisites································································································ 212
Configuration guidelines ··································································································· 212
Configuration procedure ··································································································· 213
Displaying and maintaining GRE······························································································· 213
GRE over IPv4 tunnel configuration example ··············································································· 214
GRE over IPv6 tunnel configuration example ··············································································· 217
Troubleshooting GRE ············································································································· 221
Document conventions and icons ···················································· 222
Conventions ························································································································· 222
Network topology icons ··········································································································· 223
Support and other resources ·························································· 224
Accessing Hewlett Packard Enterprise Support ············································································ 224
Accessing updates················································································································· 224
Websites ······················································································································· 225
Customer self repair········································································································· 225
Remote support ·············································································································· 225
Documentation feedback ·································································································· 225
Index························································································· 227
Configuring ARP
Overview
The Address Resolution Protocol (ARP) is used to resolve an IP address into a physical address
(Ethernet MAC address, for example).
In an Ethernet LAN, a device uses ARP to resolve the IP address of the next hop to the
corresponding MAC address.
ARP message format
ARP messages include ARP requests and ARP replies. Figure 1 shows the format of the ARP
request/reply. Numbers in the figure refer to field lengths.
Figure 1 ARP message format
ARP message fields:
•Hardware type—The hardware address type. Value 1 represents Ethernet.
•Protocol type—The 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 type of the 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 operation
If Host A and Host B are on the same subnet and Host A sends a packet to Host B, as shown
in Figure 2, the resolution process is:
1. Host A looks in its ARP table to see whether there is an ARP entry for Host B. If yes, Host A
uses the MAC address in the entry to encapsulate the IP packet into a data link layer frame and
sends the frame to Host B.
1
2. If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an ARP request
using the following information:
{Source IP address and source MAC address—Host A’s own IP address and the 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 to its ARP table.
b. Encapsulates the MAC address into the packet and sends it to Host B.
Figure 2 ARP address resolution process
If Host A and Host B are on different subnets, the resolution process is as follows:
1. Host A sends an ARP request to the gateway. The target IP address in the ARP request is the
IP address of the gateway.
2. After obtaining the MAC address of the gateway from an ARP reply, Host A sends the packet to
the gateway.
3. If the gateway maintains the ARP entry of Host B, it forwards the packet to Host B directly; if not,
it broadcasts an ARP request, in which the target IP address is the IP address of Host B.
4. After obtaining the MAC address of Host B, the gateway 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 theoutput interface goes down, and it can be overwritten by a static ARPentry.
Static ARP entry
A static ARP entry is manually configured and maintained. It does not age out, and cannot be
overwritten by a dynamicARP entry.
2
Static ARP entries protect communication between devices, because attack packets cannot modify
the IP-to-MAC mapping in a staticARP entry.
Static ARP entries can be classified into long, and shortARP entries.
•To configure a long static ARP entry, specify the IP address, MAC address, VLAN, and output
interface. A long static ARP entry is directly used for forwarding matching packets. To allow
communication with a host using a fixed IP-to-MAC mapping through a specific interface in a
specific VLAN, configure a long static ARP entry for it.
•To configure a short static ARP entry, you only need to specify the IP address and MAC
address.
If the output interface is a VLAN interface, the device first sends anARP 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 receiving theARP reply to the short staticARP entry, and then uses the
resolved entry to forward the matching IP packets.
To communicate with a host by using a fixed IP-to-MAC mapping, configure a short static ARP
entry for it.
Configuring a static ARP entry
A static ARP entry is effective when the device it corresponds to works properly. However, when a
VLAN or VLAN interface is deleted, any static ARP entry corresponding to it will also be deleted (if it
is a long static ARP entry) or will become unresolved (if it is a short and resolved staticARP entry).
Follow these guidelines when you configure a long 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
2. Configure a static ARP
entry.
•Configure a long static ARP entry:
arp static ip-address mac-address vlan-id
interface-type interface-number
•Configure a short static ARP entry:
arp static ip-address mac-address
Use either command.
Configuring the maximum number of dynamic
ARP entries for an interface
An interface can dynamically learnARP entries. To prevent an interface from holding too many ARP
entries, you can set the maximum number of dynamic ARPentries that an interface can learn. When
the maximum number is reached, the interface stops learningARP entries.
3
A 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 that an interface can learn:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter Ethernet interface view. interface interface-type
interface-number N/A
3. Set the maximum number of
dynamic ARP entries that the
interface can learn.
arp max-learning-num
number
Optional.
By default, a Layer 2 interface does not
limit the number of dynamic ARP
entries. A Layer 3 interface on the HPE
3100 48 v2 Switch can learn up to 2048
dynamic ARP entries.
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 aging timer. The aging timer
of a dynamic ARP entry is reset each time the dynamic ARP entry is updated. Dynamic ARP entries
that are not updated before their aging timers expire are deleted from theARP table.
To set the age timer for dynamic ARP entries:
Step Command Remarks
1. Enter system view. system-view N/A
2. Set the age timer for dynamic
ARP entries. arp timer aging aging-time Optional.
20 minutes by default.
Enabling dynamic ARP entry check
The dynamic ARP entry check function controls whether the device supports dynamic ARP entries
with multicast MAC addresses.
When dynamic ARPentry check is enabled, the devicecannot learn dynamic ARPentries containing
multicast MAC addresses.
When dynamic ARP entry check is disabled, the device can learn dynamic 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 Optional.
Enabled by default.
4
Configuring ARP quick update
Hewlett Packard Enterprise recommends you enable ARP quick update in WLAN networks only.
As shown in Figure 3, the laptop frequently roams betweenAP 1 and AP 2. This affects the mapping
between its MAC address and output interface on the switch. If the switch does not update its ARP
table immediately after the output interface changes, it might fail to communicate with the laptop.
Figure 3 ARP quick update application scenario
With ARP quick update enabled, the switch updates the correspondingARP entry immediately after
the change of the mapping between a MAC address and an output interface to ensure nonstop data
forwarding.
To enable ARP quick update:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable ARP quick
update. mac-address station-move
quick-notify enable Optional.
Disabled by default.
Configuring multicast ARP
Microsoft Network Load Balancing (NLB) is a load balancing technology for server clustering
developed on Windows Server.
NLB supports load sharing and redundancy among servers within a cluster. To implement fast
failover, NLB requires that the switch forwards network traffic to all servers or specified servers in the
cluster, and each server filters out unexpected traffic. In a medium or small data center that uses the
Windows Server operating system, the proper cooperation of the switch and NLB is very important.
For more information about NLB, see the related documents of Windows Sever.
Microsoft NLB provides the following packet sending modes to make the switch forward network
traffic to all servers or specified servers:
•Unicast mode—NLB assigns each cluster member a common MAC address, which is the
cluster MAC address, and changes the source MAC address of each sent packet. Thus, the
switch cannot add the cluster MAC address to its MAC table. In addition, because the cluster
MAC address is unknown to the switch, packets destined to it are forwarded on all the ports of
the switch.
•Multicast mode—NLB uses a multicast MAC address that is a virtual MAC address for network
communication, for example 0300-5e11-1111.
5
NOTE:
Multicast ARP is applicable to only multicast-mode NLB.
To configure multicast ARP:
Step Command Remarks
1. Disable the ARP entry
check function. undo arp check enable N/A
2. Configure a static ARP
entry. arp static ip-address mac-address
vlan-id interface-type
interface-number Optional.
3. Configure a static multicast
MAC address entry. mac-address multicast
mac-address interface interface-list
vlan vlan-id
See IP Multicast Command
Reference.
Displaying and maintaining ARP
CAUTION:
Clearing ARP entries from the ARP table might cause communication failures.
Task Command Remarks
Display ARP entries in the ARP
table.
display arp [ [ all | dynamic | static ] [ slot
slot-number ] | vlan vlan-id | interface
interface-type interface-number ] [ count |
verbose ] [ |{ begin | exclude | include }
regular-expression ]
Available in any view
Display the ARP entry for a
specified IP address.
display arp ip-address [slot slot-number ]
[verbose ] [ | {begin |exclude |include }
regular-expression ] Available in any view
Display the age timer for dynamic
ARP entries. display arp timer aging [ |{ begin | exclude
| include } regular-expression ] Available in any view
Clear ARP entries from the ARP
table.
reset arp { all | dynamic | static | slot
slot-number | interface interface-type
interface-number }
Available in user view
ARP configuration examples
Static ARP entry configuration example
Network requirements
As shown in Figure 4, hosts are connected to the switch, which is connected to the router through
interface Ethernet 1/0/1 in VLAN 10. The IP and MAC addresses of the router are 192.168.1.1/24
and 00e0-fc01-0000 respectively.
To prevent malicious users from attacking the switch and enhance security for communications
between the router and switch, configure a static ARP entry for the router on the switch.
6
Figure 4 Network diagram
Configuration procedure
Configure the switch:
# Create VLAN 10.
<Switch> system-view
[Switch] vlan 10
[Switch-vlan10] quit
# Add interface Ethernet 1/0/1 to VLAN 10.
[Switch] interface Ethernet 1/0/1
[Switch-Ethernet1/0/1] port link-type trunk
[Switch-Ethernet1/0/1] port trunk permit vlan 10
[Switch-Ethernet1/0/1] quit
# Create interface VLAN-interface 10 and configure its IP address.
[Switch] interface vlan-interface 10
[Switch-vlan-interface10] ip address 192.168.1.2 24
[Switch-vlan-interface10] quit
# Configure a static ARP entry that has IP address 192.168.1.1, MAC address 00e0-fc01-0000, and
output interface Ethernet 1/0/1 in VLAN 10.
[Switch] arp static 192.168.1.1 00e0-fc01-0000 10 Ethernet 1/0/1
# Display information about staticARP entries.
[Switch] display arp static
Type: S-Static D-Dynamic A-Authorized
IP Address MAC Address VLAN ID Interface Aging Type
192.168.1.1 00e0-fc01-0000 10 Eth1/0/1 N/A S
Multicast ARP configuration example
Network requirements
As shown in Figure 5, a small data center uses Microsoft multicast-mode NLB. To enable the
switches to cooperate with NLB, configure the following:
•Add Ethernet 1/0/2 and Ethernet 1/0/3 into VLAN 1, and specify IP address 16.1.1.30/24 for
VLAN-interface 1.
7
•Add Ethernet 1/0/1 and Ethernet 1/0/4 into VLAN 2, and specify IP address 17.1.1.1/24 for
VLAN-interface 2.
•Specify 17.1.1.1/24 as the default gateway of HostA and Host B.
•Specify 16.1.1.30/24 as the default gateway of Server A and Server B.
•Disable the ARP entry check function so that the switch can learn dynamic ARP entries
containing multicast MAC addresses.
•Configure a static multicast MAC address entry so that only interfaces Ethernet 1/0/2 and
Ethernet 1/0/3 can receive multicast information.
Figure 5 Network diagram
Configuration procedure
This example only describes multicast ARP configuration on the switch, and is only applicable to
multicast NLB. For NLB configuration on the servers, see the related documents of the Windows
Server.
# Specify an IP address for VLAN-interface 2.
<Switch> system-view
[Switch] vlan 2
[Switch-vlan2] port Ethernet 1/0/4
[Switch-vlan2] port Ethernet 1/0/1
[Switch-vlan2] quit
[Switch] interface vlan-interface 2
[Switch-Vlan-interface2] ip address 17.1.1.1 255.255.255.0
[Switch-Vlan-interface2] quit
# Specify an IP address for VLAN-interface 1.
[Switch] interface vlan-interface 1
[Switch-Vlan-interface1] ip address 16.1.1.30 255.255.255.0
[Switch-Vlan-interface1] quit
# Disable the ARP entry check function.
[Switch] undo arp check enable
# Configure a static multicast MAC address entry.
[Switch] mac-address multicast 03bf-1001-0164 interface Ethernet 1/0/2 Ethernet 1/0/3 vlan
1
Verifying the configuration
•NLB load sharing—Enables the FTP server function of Server A and Server B. Host A and
Host B send requests to the virtual IP address and each of them logs in to a different server.
8
9
•NLB redundancy—Disables the network interface card of Server A. Host A and Host B send
requests to the virtual IP address and both log in to the FTP server on Server B.
Configuring gratuitous ARP
Overview
In a gratuitous ARP packet, the sender IP address and the target IP address are the IP address of
the sending device.
A device sends a gratuitous ARP packet for either of the following purposes:
•Determine whether its IPaddress is already used by another device. If the IPaddress is already
used, the device is informed of the conflict by anARP reply.
•Inform other devices of a change of its MAC address.
Gratuitous ARP packet learning
This feature enables a device to create or update ARP entries by using the sender IP and MAC
addresses in received gratuitous ARP packets.
With this feature disabled, the device uses received gratuitousARP packets to update existing ARP
entries only.
Periodic sending of gratuitous ARP packets
Enabling a device to periodically send gratuitous ARP packets helps downstream devices update
their correspondingARP entries or MAC entries in time. This feature can be used to:
•Prevent gateway spoofing.
When an attacker sends forged gratuitous ARP packets to the hosts on a network, the traffic
destined for the gateway from the hosts is sent to the attacker instead. As a result, the hosts
cannot access the external network.
To prevent gateway spoofing attacks, enable the gateway to send gratuitous ARP packets
containing its primary IP address and manually configured secondary IP addresses at a specific
interval, so hosts can learn correct gateway address information.
•Prevent ARP entries from aging out.
If network traffic is heavy or if a host’s CPU usage is high on a host, received ARP packets
might be discarded or not be processed in time. Eventually, the dynamic ARP entries on the
receiving host age out, and the traffic between the host and the corresponding devices is
interrupted until the host re-creates the ARP entries.
To prevent this problem, enable the gateway to send gratuitous ARP packets periodically. The
gratuitous ARP packets contain the gateway's primary IP address or one of its manually
configured secondary IP addresses, so the receiving host can update ARP entries in time,
ensuring traffic continuity.
Configuration guidelines
Follow these guidelines when you configure gratuitousARP:
•You can enable periodic sending of gratuitous ARP packets in VLAN interface view.
•You can enable periodic sending of gratuitousARP packets on a maximum of 1024 interfaces.
•Periodic sending of gratuitous ARP packets takes effect only when the link of the enabled
interface goes up and an IP address has been assigned to the interface.
10
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