HP 6125XLG User manual
HP 6125XLG Blade Switch
Layer 3 - IP Services
Configuration Guide
Part number: 5998-5371a
Software version: Release 240x
Document version: 6W101-20150515
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Contents
Configuring ARP··························································································································································· 1
Overview············································································································································································1
ARP message format ················································································································································1
ARP operating mechanism ······································································································································1
ARP table···································································································································································2
Configuring a static ARP entry·········································································································································3
Configuring a multiport ARP entry···································································································································4
Setting the maximum number of dynamic ARP entries for a device ············································································5
Setting the maximum number of dynamic ARP entries for an interface ······································································5
Setting the aging timer for dynamic ARP entries ···········································································································6
Enabling dynamic ARP entry check ································································································································6
Enabling ARP logging·······················································································································································6
Configuring ARP fast update ···········································································································································7
Displaying and maintaining ARP·····································································································································8
Configuration examples ···················································································································································8
Static ARP configuration example ··························································································································8
Multiport ARP entry configuration example···········································································································9
Configuring gratuitous ARP ·······································································································································12
Overview········································································································································································· 12
Gratuitous ARP packet learning··························································································································· 12
Periodic sending of gratuitous ARP packets ······································································································· 12
Configuration procedure··············································································································································· 13
Enabling IP conflict notification ···································································································································· 13
Configuring proxy ARP··············································································································································15
Enabling common proxy ARP ······································································································································· 15
Enabling local proxy ARP·············································································································································· 15
Displaying proxy ARP···················································································································································· 16
Common proxy ARP configuration example··············································································································· 16
Network requirements··········································································································································· 16
Configuration procedure ······································································································································ 16
Configuring ARP snooping········································································································································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 ······················································································································ 21
Configuration guidelines ······································································································································ 21
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
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Network requirements··········································································································································· 23
Configuration procedure ······································································································································ 23
Verifying the configuration··································································································································· 24
DHCP overview ··························································································································································25
DHCP address allocation ·············································································································································· 25
Allocation mechanisms ········································································································································· 25
IP address allocation process······························································································································· 26
IP address lease extension···································································································································· 26
DHCP message format··················································································································································· 27
DHCP options ································································································································································· 28
Common DHCP options········································································································································ 28
Custom DHCP options··········································································································································· 28
Protocols and standards ················································································································································ 30
Configuring the DHCP server····································································································································32
Overview········································································································································································· 32
DHCP address pool··············································································································································· 32
IP address allocation sequence···························································································································· 34
DHCP server configuration task list ······························································································································ 34
Configuring an address pool on the DHCP server····································································································· 35
Configuration task list ··········································································································································· 35
Creating a DHCP address pool··························································································································· 35
Specifying IP address ranges for a DHCP address pool ·················································································· 35
Specifying gateways for the client······················································································································· 38
Specifying a domain name suffix for the client·································································································· 39
Specifying DNS servers for the client·················································································································· 39
Specifying WINS servers and NetBIOS node type for the client····································································· 39
Specifying BIMS server information for the client ······························································································ 40
Specifying the TFTP server and boot file name for the client············································································ 40
Specifying a server for the DHCP client·············································································································· 41
Configuring Option 184 parameters for the client···························································································· 41
Customizing DHCP options ·································································································································· 42
Enabling DHCP ······························································································································································ 43
Enabling the DHCP server on an interface·················································································································· 43
Applying an address pool on an interface ················································································································· 44
Configuring IP address conflict detection···················································································································· 44
Enabling handling of Option 82·································································································································· 44
Configuring DHCP server compatibility······················································································································· 45
Configuring the DHCP server to broadcast all responses················································································· 45
Configure the DHCP server to ignore BOOTP requests ···················································································· 45
Configuring the DHCP server to send BOOTP responses in RFC 1048 format·············································· 46
Setting the DSCP value for DHCP packets sent by the DHCP server········································································ 46
Displaying and maintaining the DHCP server ············································································································ 46
DHCP server configuration examples ·························································································································· 47
Static IP address assignment configuration example························································································· 47
Dynamic IP address assignment configuration example··················································································· 49
DHCP user class configuration example············································································································· 50
Primary and secondary subnets configuration example ··················································································· 51
DHCP option customization configuration example·························································································· 52
Troubleshooting DHCP server configuration ··············································································································· 53
Symptom································································································································································· 53
Analysis ·································································································································································· 53
Solution··································································································································································· 54
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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 ······································································································································ 66
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
Setting the maximum number of DHCP snooping entries ·························································································· 75
Configuring DHCP packet rate limit····························································································································· 75
Displaying and maintaining DHCP snooping ············································································································· 76
DHCP snooping configuration examples····················································································································· 77
Basic DHCP snooping configuration example ··································································································· 77
Option 82 configuration example······················································································································· 77
Configuring the BOOTP client···································································································································79
BOOTP application························································································································································ 79
Obtaining an IP address dynamically ························································································································· 79
Protocols and standards ················································································································································ 79
iv
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
Setting the DSCP value for outgoing DNS packets ···································································································· 89
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······················································································································ 93
IPv6 DNS configuration examples ······························································································································· 95
Static domain name resolution configuration example ····················································································· 95
Dynamic domain name resolution configuration example ··············································································· 96
DNS proxy configuration example····················································································································100
Troubleshooting IPv4 DNS configuration ··················································································································101
Symptom·······························································································································································101
Solution·································································································································································101
Troubleshooting IPv6 DNS configuration ··················································································································101
Symptom·······························································································································································101
Solution·································································································································································101
Configuring DDNS·················································································································································· 102
Overview·······································································································································································102
DDNS application ···············································································································································102
DDNS client configuration task list·····························································································································103
Configuring a DDNS policy········································································································································103
Configuration prerequisites ································································································································105
Configuration procedure ····································································································································105
Applying the DDNS policy to an interface················································································································105
Setting the DSCP value for outgoing DDNS packets································································································106
Displaying DDNS·························································································································································106
DDNS configuration examples ···································································································································107
DDNS configuration example with www.3322.org ·······················································································107
DDNS configuration example with PeanutHull server·····················································································108
Basic IP forwarding on the device ························································································································· 110
FIB table ········································································································································································110
v
Displaying FIB table entries·········································································································································110
Configuring load sharing ······································································································································· 112
Overview·······································································································································································112
Configuring load sharing ············································································································································112
Enabling local-first load sharing·································································································································112
Load sharing configuration example ·························································································································113
Network requirements·········································································································································113
Configuration procedure ····································································································································113
Verifying the configuration·································································································································114
Configuring IRDP····················································································································································· 115
Overview·······································································································································································115
IRDP operation·····················································································································································115
Basic concepts ·····················································································································································116
Protocols and standards ·····································································································································116
Configuration procedure·············································································································································116
IRDP configuration example········································································································································117
Network requirements·········································································································································117
Configuration procedure ····································································································································118
Verifying the configuration·································································································································119
Optimizing IP performance ···································································································································· 120
Enabling an interface to receive and forward directed broadcasts destined for the directly connected network
·······················································································································································································120
Configuration procedure ····································································································································120
Configuration example ·······································································································································121
Configuring MTU for an interface ······························································································································121
Configuring TCP MSS for an interface ······················································································································122
Configuring TCP path MTU discovery ·······················································································································122
Enabling TCP SYN Cookie··········································································································································123
Configuring the TCP buffer size··································································································································124
Configuring TCP timers················································································································································124
Enabling sending ICMP error messages····················································································································124
Disabling forwarding ICMP fragments ······················································································································126
Configuring rate limit for ICMP error messages ·······································································································126
Specifying the source address for ICMP packets ·····································································································126
Configuring IP virtual fragment reassembly ··············································································································127
Configuration guidelines ····································································································································127
Configuration procedure ····································································································································127
Displaying and maintaining IP performance optimization ······················································································128
Configuring UDP helper·········································································································································· 129
Overview·······································································································································································129
Configuration guidelines ·············································································································································129
Configuration procedure·············································································································································129
Displaying and maintaining UDP helper ···················································································································130
UDP helper configuration example ····························································································································130
Network requirements·········································································································································130
Configuration procedure ····································································································································130
Verifying the configuration·································································································································131
Configuring basic IPv6 settings······························································································································ 132
Overview·······································································································································································132
IPv6 features·························································································································································132
IPv6 addresses·····················································································································································133
IPv6 ND protocol·················································································································································136
vi
IPv6 path MTU discovery····································································································································138
IPv6 transition technologies·········································································································································138
Dual stack·····························································································································································139
Tunneling······························································································································································139
Protocols and standards ··············································································································································139
IPv6 basics configuration task list·······························································································································139
Assigning IPv6 addresses to interfaces······················································································································140
Configuring an IPv6 global unicast address ····································································································140
Configuring an IPv6 link-local address ·············································································································142
Configuring an IPv6 anycast address ···············································································································143
Configuring IPv6 ND ···················································································································································144
Configuring a static neighbor entry ··················································································································144
Setting the maximum number of dynamic neighbor entries············································································144
Setting the aging timer for ND entries in stale state························································································145
Minimizing link-local ND entries························································································································145
Setting the hop limit ············································································································································145
Configuring parameters for RA messages········································································································146
Configuring the maximum number of attempts to send an NS message for DAD·······································148
Enabling ND proxy ·············································································································································148
Configuring a customer-side port ·······························································································································150
Configuring path MTU discovery ·······························································································································150
Configuring the interface MTU ··························································································································150
Configuring a static path MTU for a specific IPv6 address ············································································151
Configuring the aging time for dynamic path MTUs·······················································································151
Controlling sending ICMPv6 messages ·····················································································································151
Configuring the rate limit for ICMPv6 error messages····················································································152
Enabling replying to multicast echo requests ···································································································152
Enabling sending ICMPv6 destination unreachable messages······································································152
Enabling sending ICMPv6 time exceeded messages······················································································153
Enabling sending ICMPv6 redirect messages ··································································································153
Specifying the source address for ICMPv6 packets ························································································154
Enabling a device to discard IPv6 packets that contain extension headers··························································154
Displaying and maintaining IPv6 basics ···················································································································154
Basic IPv6 configuration example ······························································································································156
Network requirements·········································································································································156
Configuration procedure ····································································································································156
Verifying the configuration·································································································································157
Troubleshooting IPv6 basics configuration················································································································160
Symptom·······························································································································································160
Solution·································································································································································160
DHCPv6 overview··················································································································································· 161
DHCPv6 address/prefix assignment··························································································································161
Rapid assignment involving two messages·······································································································161
Assignment involving four messages·················································································································161
Address/prefix lease renewal ····································································································································162
Stateless DHCPv6·························································································································································163
Protocols and standards ··············································································································································163
Configuring the DHCPv6 server····························································································································· 164
Overview·······································································································································································164
IPv6 address assignment ····································································································································164
IPv6 prefix assignment········································································································································164
Concepts·······························································································································································165
DHCPv6 address pool ········································································································································166
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IPv6 address/prefix allocation sequence ·········································································································167
Configuration task list ··················································································································································167
Configuring IPv6 prefix assignment ···························································································································167
Configuration guidelines ····································································································································168
Configuration procedure ····································································································································168
Configuring IPv6 address assignment························································································································169
Configuration guidelines ····································································································································169
Configuration procedure ····································································································································169
Configuring network parameters assignment ···········································································································170
Configuring the DHCPv6 server on an interface ······································································································171
Configuration guidelines ····································································································································171
Configuration procedure ····································································································································171
Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 server ·····························································172
Displaying and maintaining the DHCPv6 server ······································································································172
DHCPv6 server configuration examples····················································································································173
Dynamic IPv6 prefix assignment configuration example ················································································173
Dynamic IPv6 address assignment configuration example·············································································175
Configuring the DHCPv6 relay agent···················································································································· 178
Overview·······································································································································································178
Configuration guidelines ·············································································································································179
Configuration procedure·············································································································································179
Displaying and maintaining the DHCPv6 relay agent·····························································································180
DHCPv6 relay agent configuration example ············································································································180
Network requirements·········································································································································180
Configuration procedure ····································································································································180
Verifying the configuration·································································································································181
Configuring the DHCPv6 client······························································································································ 182
Overview·······································································································································································182
DHCPv6 client configuration task list·························································································································182
Configuring IPv6 address acquisition ························································································································182
Configuring IPv6 prefix acquisition····························································································································183
Configuring stateless DHCPv6····································································································································183
Setting the DSCP value for DHCPv6 packets sent by the DHCPv6 client·······························································184
Configuring the DHCPv6 client DUID ························································································································184
Displaying and maintaining DHCPv6 client··············································································································185
DHCPv6 client configuration examples ·····················································································································185
IPv6 address acquisition configuration example ·····························································································185
IPv6 prefix acquisition configuration example·································································································187
Stateless DHCPv6 configuration example ········································································································188
Configuring DHCPv6 snooping ····························································································································· 191
Overview·······································································································································································191
Application of trusted and untrusted ports········································································································191
HP implementation of Option 18 and Option 37 ····································································································192
Option 18 for DHCPv6 snooping······················································································································192
DHCPv6 snooping support for Option 37········································································································193
DHCPv6 snooping configuration task list ··················································································································193
Configuring basic DHCPv6 snooping························································································································194
Configuring Option 18 and Option 37 ····················································································································194
Saving DHCPv6 snooping entries ······························································································································195
Setting the maximum number of DHCPv6 snooping entries····················································································196
Enabling DHCPv6-REQUEST check····························································································································196
Configuring DHCPv6 packet rate limit ······················································································································197
Displaying and maintaining DHCPv6 snooping·······································································································197
viii
DHCPv6 snooping configuration example················································································································198
Network requirements·········································································································································198
Configuration procedure ····································································································································198
Verifying the configuration·································································································································199
Configuring tunneling ············································································································································· 200
Overview·······································································································································································200
IPv6 over IPv4 tunneling ·····································································································································200
IPv4 over IPv4 tunneling ·····································································································································202
IPv4 over IPv6 tunneling ·····································································································································203
IPv6 over IPv6 tunneling ·····································································································································204
Protocols and standards ·····································································································································204
Tunneling configuration task list ·································································································································205
Configuring a tunnel interface····································································································································205
Configuring an IPv6 over IPv4 manual tunnel···········································································································206
Configuration example ·······································································································································207
Configuring a 6to4 tunnel···········································································································································209
Configuration example ·······································································································································210
Configuring an ISATAP tunnel ····································································································································212
Configuration example ·······································································································································213
Configuring an IPv4 over IPv4 tunnel ························································································································215
Configuration example ·······································································································································216
Configuring an IPv4 over IPv6 tunnel ························································································································218
Configuration example ·······································································································································219
Configuring an IPv6 over IPv6 tunnel ························································································································221
Configuration example ·······································································································································222
Displaying and maintaining tunneling·······················································································································224
Troubleshooting tunneling ···········································································································································224
Symptom·······························································································································································224
Analysis ································································································································································225
Solution·································································································································································225
Configuring GRE····················································································································································· 226
Overview·······································································································································································226
GRE encapsulation format··································································································································226
GRE tunnel operating principle··························································································································227
Protocols and standards ·····································································································································227
Configuring a GRE over IPv4 tunnel ··························································································································227
Configuring a GRE over IPv6 tunnel ··························································································································229
Displaying and maintaining GRE·······························································································································231
GRE configuration examples ······································································································································232
GRE over IPv4 tunnel configuration example···································································································232
GRE over IPv6 tunnel configuration example···································································································234
Troubleshooting GRE ···················································································································································237
Symptom·······························································································································································237
Analysis ································································································································································237
Solution·································································································································································238
Support and other resources ·································································································································· 239
Contacting HP ······························································································································································239
Subscription service ············································································································································239
Related information······················································································································································239
Documents····························································································································································239
Websites·······························································································································································239
Conventions ··································································································································································240
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 contains 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, static, and OpenFlow 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.
The device supports the following types of static ARP entries:
•Long static ARP entry—It contains the IP address, MAC address, VLAN, and output interface. It is
directly used for forwarding packets.
•Short static ARP entry—It contains 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 short static ARP entry, the device performs the following operations:
−Adds the interface that received the ARP reply to the short static ARP entry.
−Uses the resolved short static ARP entry to forward IP packets.
•Multiport ARP entry—It contains the IP address, MAC address, and VLAN.
The device can use a multiport ARP entry that has the same MAC address and VLAN as a multicast
or multiport unicast MAC address entry for packet forwarding. A multiport ARP entry is manually
configured. It does not age out and cannot be overwritten by any dynamic ARP entry. For more
information about multicast MAC, see IP Multicast Configuration Guide.
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.
OpenFlow ARP entry
ARP creates OpenFlow ARP entries by learning from the OpenFlow module. An OpenFlow ARP entry
does not age out, and it cannot be updated unless a static ARP entry overwrites it. An OpenFlow ARP
entry can be used directly to forward packets. For more information about OpenFlow, see OpenFlow
Configuration Guide.
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.
4
•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
[ 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.
Configuring a multiport ARP entry
A multiport ARP entry contains an IP address, MAC address, and VLAN ID. To make the multiport ARP
entry effective for packet forwarding, you must configure a multicast or multiport unicast MAC address
entry to specify multiple output interfaces. The MAC address entry must have the same MAC address and
VLAN ID as the multiport ARP entry. In addition, the IP address in the multiport ARP entry must reside on
the same subnet as the VLAN interface of the specified VLAN.
A multiport ARP entry can overwrite a dynamic, short static or long static ARP entry. Conversely, a short
static or long static ARP entry can overwrite a multiport ARP entry.
When you configure multiport ARP entries in Release 2406P03 and later versions, you must first create
a service loopback group to support the multiport ARP service. The service loopback group loops packets
whose destination IP addresses match multiport ARP entries back to the forwarding module. Then the
forwarding module looks up the multiport MAC address table for output interfaces. For information about
creating and configuring a service loopback group, see Layer 2—LAN Switching Configuration Guide.
To configure a multiport ARP entry:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure a multicast or
multiport unicast MAC
address entry.
•Configure a multiport unicast MAC
address entry:
mac-address multiport mac-address
interface interface-list vlan vlan-id
•Configure a multicast MAC address
entry:
mac-address multicast mac-address
interface interface-list vlan vlan-id
By default, no multicast or
multiport unicast MAC address
entries are configured.
For more information about the
mac-address multiport
command, see Layer 2—LAN
Switching Command Reference.
For more information about the
mac-address multicast command,
see IP Multicast Command
Reference.
5
Step Command Remarks
3. Configure a multiport ARP
entry.
arp multiport ip-address mac-address
vlan-id [ vpn-instance
vpn-instance-name ]
By default, no multiport ARP
entries are 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. The device also 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
By default, a device can learn a maximum of
16384 dynamic ARP entries.
To disable the device from learning dynamic
ARP entries, set the number to 0.
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
1. Enter system view. system-view N/A
2. Enter interface view. interface interface-type
interface-number N/A
6
Step Command Remarks
3. Set the maximum number of
dynamic ARP entries for the
interface.
arp max-learning-num number
By default, an interface can learn a
maximum of 16384 dynamic ARP
entries.
To disable the interface from learning
dynamic ARP entries, set the number to
0.
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 logging
This function enables a device to log ARP events when ARP cannot resolve IP addresses correctly. The
events include the following:
7
•On a proxy ARP-disabled interface, the target IP address of a received ARP packet is not one of the
following IP addresses:
{The IP address of the receiving interface.
{The virtual IP address of the VRRP group.
{The NATed external address.
•The sender IP address of a received ARP reply conflicts with one of the following IP addresses:
{The IP address of the receiving interface.
{The virtual IP address of the VRRP group.
{The NATed external address.
The device sends ARP log messages to the information center. You can use the info-center source
command to specify the log output rules for the information center. For more information about
information center, see Network Management and Monitoring Configuration Guide.
To enable the ARP logging function:
Ste
p
Command
Remarks
1. Enter system view. system-view N/A
2. Enable the ARP logging
function. arp check log enable By default, ARP logging is disabled.
Configuring ARP fast update
ARP fast update for MAC move allows the device to update an ARP entry immediately after the output
interface for a MAC address changes. This feature ensures data connection without interruption.
In a network as shown in Figure 3,a mobile user Laptop accesses the network by connecting to AP 1 or
AP 2. When the AP to which the user connects changes, the switch updates the ARP entry for the user
immediately after it detects a MAC move event.
Figure 3 ARP fast update application scenario
To enable ARP fast update for MAC move:
Step Command Remarks
1. Enter system view. system-view N/A
8
Step Command Remarks
2. Enable ARP fast
update.
mac-address mac-move
fast-update
By default, ARP fast update is disabled for
MAC move.
Displaying and maintaining ARP
IMPORTANT:
Clearing ARP entries from the ARP table might cause communication failures. Make sure the entries to be
cleared do not affect current communications.
Execute display commands in any view and reset commands in user view.
Task Command
Display ARP entries.
display arp [ [ all | dynamic | multiport | static ] [ slot
slot-number ] | vlan vlan-id | interface interface-type
interface-number ] [ count | verbose ]
Display the ARP entry for a specified IP
address. display arp ip-address [slot slot-number ] [ verbose ]
Display the ARP entries for a specified VPN
instance. display arp vpn-instance vpn-instance-name [ count ]
Display the aging timer of dynamic ARP
entries. display arp timer aging
Clear ARP entries from the ARP table. reset arp { all | dynamic | interface interface-type
interface-number |multiport | slot slot-number | static }
Configuration examples
Static ARP configuration example
Network requirements
As shown in Figure 4, hosts are connected to the switch, which is connected to the router through
interface Ten-GigabitEthernet 1/1/5 in VLAN 10.
To ensure secure communications between the router and switch, configure a static ARP entry for the
router on the switch.
9
Figure 4 Network diagram
Configuration procedure
# Create VLAN 10.
<Switch> system-view
[Switch] vlan 10
[Switch-vlan10] quit
# Add interface Ten-GigabitEthernet 1/1/5 to VLAN 10.
[Switch] interface Ten-GigabitEthernet 1/1/5
[Switch-Ten-GigabitEthernet1/1/5] port access vlan 10
[Switch-Ten-GigabitEthernet1/1/5] quit
# Create VLAN-interface 10 and configure its IP address.
[Switch] interface vlan-interface 10
[Switch-vlan-interface10] ip address 192.168.1.2 8
[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 Ten-GigabitEthernet 1/1/5 in VLAN 10.
[Switch] arp static 192.168.1.1 00e0-fc01-0000 10 Ten-GigabitEthernet 1/1/5
# Display information about static ARP entries.
[Switch] display arp static
Type: S-Static D-Dynamic O-Openflow M-Multiport I-Invalid
IP address MAC address VLAN Interface Aging Type
192.168.1.1 00e0-fc01-0000 10 XGE1/1/5 N/A S
Multiport ARP entry configuration example
Network requirements
As shown in Figure 5, a switch connects to three servers through interfaces Ten-GigabitEthernet 1/1/5,
Ten-GigabitEthernet 1/1/6, and Ten-GigabitEthernet 1/1/7 in VLAN 10. The servers share the IP
address 192.168.1.1/24 and MAC address 00e0-fc01-0000.
Configure a multiport ARP entry to send IP packets with destination IP address 192.168.1.1 to the three
servers.
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