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ARP Commands
This chapter describes the commands used to configure and monitor the Address Resolution Protocol (ARP) on Cisco ASR 9000 Series Aggregation Services routers .
For detailed information about ARP concepts, configuration tasks, and examples, see the Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Configuration Guide.
- arp
- arp dagr
- arp purge-delay
- arp timeout
- clear arp-cache
- peer (DAGR)
- priority-timeout
- proxy-arp
- route distance
- route metric
- show arp
- show arp dagr
- show arp traffic
- timers (DAGR)
arp
To add a permanent entry in the Address Resolution Protocol (ARP) cache, use the arp command in global configuration mode. To remove an entry from the ARP cache, enter the no form of this command.
arp [ vrf vrf-name ] ip-address hardware-address encapsulation-type [alias]
no arp [ vrf vrf-name ] ip-address hardware-address encapsulation-type [alias]
Syntax Description
vrf
(Optional) Specifies VPN routing and forwarding (VRF) instance.
vrf-name
(Optional) VRF instance that identifies a VPN.
ip-address
IPv4 (network layer) address for which a permanent entry is added to the ARP cache. Enter the IPv4 address in a four-part dotted-decimal format that corresponds to the local data-link address (a 32-bit address).
hardware-address
Hardware (data link layer) address that the IPv4 address is linked to. Enter the local data-link address (a 48-bit address), such as 0800.0900.1834.
encapsulation-type
Encapsulation type. The encapsulation types are:
For Ethernet interfaces, this is typically the arpa keyword.
alias
(Optional) Causes the software to respond to ARP requests as if it were the owner of both the specified IP address and hardware address, whether proxy ARP is enabled or not.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
The software uses ARP cache entries to translate 32-bit IP addresses into 48-bit hardware addresses.
Because most hosts support dynamic resolution, you generally need not specify static ARP cache entries.
Static entries are permanent entries that map a network layer address (IPv4 address) to a data-link layer address (MAC address). If the alias keyword is specified when creating the entry, the interface to which the entry is attached will act as if it is the owner of the specified addresses, that is, it will respond to ARP request packets for this network layer address with the data link layer address in the entry.
The software does not respond to any ARP requests received for the specified IP address unless proxy ARP is enabled on the interface on which the request is received. When proxy ARP is enabled, the software responds to ARP requests with its own local interface hardware address.
To remove all nonstatic entries from the ARP cache, enter the clear arp-cache in EXEC mode.
Task ID
Examples
The following is an example of a static ARP entry for a typical Ethernet host:
RP/0/RSP0/CPU0:router# configure RP/0/RSP0/CPU0:router(config)# arp 192.168.7.19 0800.0900.1834 arpaarp dagr
To configure Direct Attached Gateway Redundancy (DAGR), use the arp dagr command in interface configuration mode.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
Examples
The following example enables DAGR configuration:
RP/0/RSP0/CPU0:router# configure RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/1/0/0.1 RP/0/RSP0/CPU0:router(config-if)# arp dagr RP/0/RSP0/CPU0:router(config-if-dagr)#Related Commands
Command
Description
Creates a DAGR group for a virtual IP address.
Configures the timeout for a high-priority DAGR route.
Configures the route distances for a given DAGR group.
Configures the route metrics for a given DAGR group.
Displays the operational state of all DAGR groups.
Configures the DAGR timers for sending ARP requests.
arp purge-delay
To delay purging Address Resolution Protocol (ARP) entries when an interface goes down, use the arp purge-delay command in interface configuration mode. To turn off the purge delay feature, use the no form of this command.
Syntax Description
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Use the arp purge-delay command to delay purging ARP entries when an interface goes down. If the interface comes up within the delay time, then the ARP entries are restored to prevent packet loss with Equal Cost Multipath (ECMP) configured.
Task ID
arp timeout
To specify how long dynamic entries learned on an interface remain in the Address Resolution Protocol (ARP) cache, enter the arp timeout command in interface configuration mode. To remove the arp timeout command from the configuration file and restore the system to its default condition with respect to this command, enter the no form of this command.
Syntax Description
seconds
Indicates the time, in seconds, for which an entry remains in the ARP cache. Range is 30 to 4294967295.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
This command is ignored when issued on interfaces that do not use ARP. Also, ARP entries that correspond to the local interface or that are statically configured by the user never time out.
The arp timeout command applies only to the interface that is entered. When the timeout is changed for an interface the change applies only to that interface.
The show interfaces command displays the ARP timeout value in hours:minutes:seconds, as follows:
ARP type: ARPA, ARP Timeout 04:00:00Task ID
Examples
The following example shows how to set the ARP timeout to 3600 seconds to allow entries to time out more quickly than the default:
RP/0/RSP0/CPU0:router# configure RP/0/RSP0/CPU0:router(config)# interface MgmtEth 0/RP1/CPU0/0 RP/0/RSP0/CPU0:router(config-if)# arp timeout 3600Related Commands
Command
Description
Deletes all dynamic entries from the ARP cache.
Displays the ARP cache.
show interfaces
Displays statistics for all interfaces configured on the networking device.
For information on using the show interfaces command, see the Cisco ASR 9000 Series Aggregation Services Router Cisco IOS XR software Interface and Hardware Component Command Reference.
clear arp-cache
To delete all dynamic entries from the Address Resolution Protocol (ARP) cache, clear the fast-switching cache, and clear the IP route cache, use the clear arp-cache command in EXEC mode.
Syntax Description
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
When issued without keywords or arguments, the clear arp-cache command clears all entries in the ARP cache.
Task ID
Examples
The following example shows how to remove traffic statistic entries from the ARP cache that match the specified interface:
RP/0/RSP0/CPU0:router# clear arp-cache traffic gigabitEthernet 0/1/5/1 location 0/1/CPU0The following example shows how to remove entries from the ARP cache that match the specified location:
RP/0/RSP0/CPU0:router# clear arp-cache location 0/1/CPU0peer (DAGR)
To create a Direct Attached Gateway Redundancy (DAGR) group for a virtual IP address, use the peer command in DAGR interface configuration mode.
Syntax Description
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
Examples
The following example configures a DAGR group peer:
RP/0/RSP0/CPU0:router(config-if-dagr)# peer ipv4 192.168.7.19 RP/0/RSP0/CPU0:router(config-if-dagr-peer)#priority-timeout
To configure the timer to time out a high-priority Direct Attached Gateway Redundancy (DAGR) route and reverting to normal priority, use the priority-timeout command in DAGR peer interface configuration mode.
Syntax Description
time
Time in seconds after which a high-priority route reverts to a normal priority route. The range of values is 1 to 10000.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
When this function is applied, the DAGR group configuration is updated in the database.
The new timer values take effect the next time the timer is set. No immediate timer restarts are triggered on the basis of this event.
Task ID
Examples
The following example configures a priority timeout of 25 seconds:
RP/0/RSP0/CPU0:router(config-if-dagr-peer)# priority-timeout 25 RP/0/RSP0/CPU0:router(config-if-dagr-peer)#Related Commands
proxy-arp
To enable proxy Address Resolution Protocol (ARP) on an interface, enter the proxy-arp command in interface configuration mode. To disable proxy ARP on the interface, enter the no form of this command.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
When proxy ARP is disabled, the networking device responds to ARP requests received on an interface only if one of the following conditions is met:
- The target IP address in the ARP request is the same as the interface IP address on which the request is received.
- The target IP address in the ARP request has a statically configured ARP alias.
When proxy ARP is enabled, the networking device also responds to ARP requests that meet all of the following conditions:
- The target IP address is not on the same physical network (LAN) on which the request is received.
- The networking device has one or more routes to the target IP address.
- All of the routes to the target IP address go through interfaces other than the one on which the request is received.
Using the no form of the command removes the specified command from the configuration file and restores the system to its default condition with respect to the command.
Task ID
route distance
To configure route distance for a given Direct Attached Gateway Redundancy (DAGR) group, use the route distance command in DAGR peer interface configuration mode.
Syntax Description
normal normal-distance
Sets normal route (administrative) distance. Range is 0 to 256.
priority priority-distance
Sets priority route (administrative) distance. Range is 0 to 256.
Command Default
Default for normal-distance default is 150 and the default for priority-distance is 5.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
The default setting for a priority distance takes precedence over that of a typical Internet Gateway Protocol (IGP). The normal distance setting does not.
When this setting is applied, the DAGR group is updated in the database.
Task ID
Examples
The following example configures a DAGR group peer with a normal route distance of 48 and priority route distance of 5:
RP/0/RSP0/CPU0:router(config-if-dagr-peer)# route distance normal 48 priority 5 RP/0/RSP0/CPU0:router(config-if-dagr-peer)#Related Commands
route metric
To configure normal and priority route metrics for a given Direct Attached Gateway Redundancy (DAGR) group, use the route metric command in DAGR peer interface configuration mode.
Syntax Description
normal normal-metric
Sets a normal value for routes installed in the Routing Information Base (RIB). The range of values is 0 to 256.
priority priority-metric
Sets a priority value for routes installed in the RIB. The range of values is 0 to 256.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
The route metric values are of less significance than the route distance command values. Setting a route metric allows the configuration of values for routers installed in the RIB.
When this setting is applied, the DAGR group is updated in the database.
Task ID
Examples
The following example configures a DAGR group peer with a normal metric of 48 and a priority metric of 5:
RP/0/RSP0/CPU0:router(config-if-dagr-peer)# route metric normal 48 priority 5 RP/0/RSP0/CPU0:router(config-if-dagr-peer)#Related Commands
show arp
Syntax Description
vrf
(Optional) Specifies VPN routing and forwarding (VRF) instance.
vrf-name
(Optional) VRF instance that identifies a VPN.
ip-address
(Optional) The ARP entries you want to display.
hardware-address
(Optional) The ARP entries that match the 48-bit MAC address are displayed.
interface- path-id
(Optional) Either a physical interface instance or a virtual interface instance as follows:
- Physical interface instance. Naming notation is rack/slot/module/port and a slash between values is required as part of the notation.
- rack: Chassis number of the rack.
- slot: Physical slot number of the modular services card or line card.
- module: Module number. A physical layer interface module (PLIM) is always 0.
- port: Physical port number of the interface.
Note In references to a Management Ethernet interface located on a route processor card, the physical slot number is alphanumeric (RSP0) and the module is CPU0. Example: interface MgmtEth0/RSP0/CPU0/0.
- Virtual interface instance. Number range varies depending on interface type.
For more information about the syntax for the router, use the question mark (?) online help function.
location node-id
(Optional) Displays the ARP entry for a specific location. The node-id argument is entered in the rack/slot/module notation.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
ARP establishes correspondences between network addresses (an IP address, for example) and Ethernet hardware addresses. A record of each correspondence is kept in a cache for a predetermined amount of time and then discarded.
For show arp interface-type interface-instance form, the location node-id keyword and argument is mandatory for Bundle and VLAN-on-Bundle interfaces to indicate which location the cache entries for the bundle should be displayed. For physical interfaces, specifying the location node-id keyword and argument is optional since the interface can only exist on one node.
Task ID
Examples
The following is sample output from the show arp command with no location specified:
RP/0/RSP0/CPU0:router# show arp ------------------------------------------------------------------------------- 0/3/CPU0 ------------------------------------------------------------------------------- Address Age Hardware Addr State Type Interface 10 .4.1.1 - 000c.cfe6.3336 Interface ARPA GigabitEthernet0/3/1/3 10 .4.1.2 01:37:50 0000.c004.0102 Dynamic ARPA GigabitEthernet0/3/1/3 10 .1.4.2 - 000c.cfe6.33b5 Interface ARPA FastEthernet0/3/3/4 10 .1.0.2 - 000c.cfe6.33b1 Interface ARPA FastEthernet0/3/3/0 10 .1.0.1 00:37:56 000a.8b08.857a Dynamic ARPA FastEthernet0/3/3/0 10 .1.4.1 01:37:51 000a.8b08.857e Dynamic ARPA FastEthernet0/3/3/4 10 .11.1.1 - 000c.cfe6.32fa Interface ARPA FastEthernet0/3/0/6 10 .1.5.2 - 000c.cfe6.33b6 Interface ARPA FastEthernet0/3/3/5 10 .1.1.2 - 000c.cfe6.33b2 Interface ARPA FastEthernet0/3/3/1 10 .1.1.1 01:37:51 000a.8b08.857b Dynamic ARPA FastEthernet0/3/3/1 10 .1.5.1 01:37:50 000a.8b08.857f Dynamic ARPA FastEthernet0/3/3/5 ------------------------------------------------------------------------------- 0/2/CPU0 ------------------------------------------------------------------------------- Address Age Hardware Addr State Type Interface 10 .6.9.1 01:11:55 0003.fe4c.0bff Dynamic ARPA MgmtEth0/2/CPU0/0 10 .6.25.6 01:09:29 000c.cfe6.2000 Dynamic ARPA MgmtEth0/2/CPU0/0 10 .6.5.10 00:39:58 0009.7b49.0bff Dynamic ARPA MgmtEth0/2/CPU0/0The following is sample output from the show arp command with the interface-type interface-instance argument:
RRP/0/RSP0/CPU0:router# show arp MgmtEth 0/RP1/CPU0/0 Address Age Hardware Addr State Type Interface 10.4.9.2 00:35:55 0030.7131.abfc Dynamic ARPA MgmtEth0/RP1/CPU0/0 10.4.9.1 00:35:55 0000.0c07.ac24 Dynamic ARPA MgmtEth0/RP1/CPU0/0 10.4.9.99 00:49:12 0007.ebea.44d0 Dynamic ARPA MgmtEth0/RP1/CPU0/0 10.4.9.199 - 0001.c9eb.dffe Interface ARPA MgmtEth0/RP1/CPU0/0The following is sample output from the show arp command with the hardware-address designation:
RP/0/RSP0/CPU0:router# show arp 0005.5f1d.8100 Address Age Hardware Addr State Type Interface 172.16.7.2 - 0005.5f1d.8100 Interface ARPA GigabitEthernet2/0/1/2The following is sample output from the show arp command with the location keyword and node-id argument:
RP/0/RSP0/CPU0:router# show arp location 0/2/CPU0 Address Age Hardware Addr State Type Interface 192.168.15.1 - 00dd.00ee.00ff Alias ARPA 192.168.13.1 - 00aa.00bb.00cc Static ARPA 172.16.7.1 00:35:49 0002.fc0e.9600 Dynamic ARPA GigabitEthernet2/0/1/2 172.16.7.2 - 0005.5f1d.8100 Interface ARPA GigabitEthernet2/0/1/2
This table describes the significant fields shown in the display.
Table 1 show arp Command Field DescriptionsField
Description
Address
Displays the network address that corresponds to the hardware address.
Age
Displays the age in hours:minutes:seconds of the cache entry. A hyphen (-) means the address is local.
Hardware Addr
Displays the LAN hardware address of a MAC address that corresponds to the network address.
State
Displays the current state of the cache entry. Values are:
Type
Displays the encapsulation type the Cisco IOS XR software is using for the network address in this entry. Value is ARPA.
Interface
Displays the interface associated with this network address.
ARP statistics
Displays ARP packet and error statistics.
ARP cache
Displays general information about the IP address and MAC address association entries in the ARP cache.
IP Packet drop count for node */*/*
Displays the number of IP packets dropped because the buffer ran out of space before an ARP response was received.
Note */*/* represents the node ID in the format rack/slot/module.
show arp dagr
To display the operational state of all Direct Attached Gateway Redundancy (DAGR) groups, use the show arp dagr command in EXEC mode.
Syntax Description
interface [IP-address]
(Optional) Restricts the output to a specific interface and virtual IP address.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Task ID
Examples
The following example shows the current operational state of the DAGR groups:
RP/0/RSP0/CPU0:router# show arp dagr -------------------------------------------------------------------------------- 0/1/CPU0 -------------------------------------------------------------------------------- Interface Virtual IP State Query-pd Dist Metr GigabitEthernet0/1/0/2 192.168.7.19 Active None 150 100 GigabitEthernet0/1/0/2 193.24.0.45 Query 1 None None GigabitEtherget0/1/0/3 192.66.0.45 Init None None NoneRelated Commands
show arp traffic
To display Address Resolution Protocol (ARP) traffic statistics, enter the show arp traffic command in EXEC mode.
Syntax Description
vrf
(Optional) Specifies VPN routing and forwarding (VRF) instance.
vrf-name
(Optional) VRF instance that identifies a VPN.
interface- path-id
(Optional) Either a physical interface instance or a virtual interface instance as follows:
- Physical interface instance. Naming notation is rack/slot/module/port and a slash between values is required as part of the notation.
- rack: Chassis number of the rack.
- slot: Physical slot number of the modular services card or line card.
- module: Module number. A physical layer interface module (PLIM) is always 0.
- port: Physical port number of the interface.
Note In references to a Management Ethernet interface located on a route processor card, the physical slot number is alphanumeric (RSP0) and the module is CPU0. Example: interface MgmtEth0/RSP0/CPU0/0.
- Virtual interface instance. Number range varies depending on interface type.
For more information about the syntax for the router, use the question mark (?) online help function.
location node-id
(Optional) Displays the ARP entry for a specific location. The node-id argument is entered in the rack/slot/module notation.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
ARP establishes correspondences between network addresses (an IP address, for example) and Ethernet hardware addresses. A record of each correspondence is kept in a cache for a predetermined amount of time and then discarded.
For show arp traffic, interface-instance, the locationnode-id keyword and argument is mandatory for Bundle and VLAN-on-Bundle interfaces to indicate which location the cache entries for the bundle should be displayed. For physical interfaces, specifying the location node-id keyword and argument is optional since the interface can only exist on one node.
Task ID
Examples
The following is sample output from the show arp traffic command:
RP/0/RSP0/CPU0:router# show arp traffic ARP statistics: Recv: 2691 requests, 91 replies Sent: 67 requests, 2 replies (0 proxy, 1 gratuitous) Resolve requests rcvd: 1 Resolve requests dropped: 0 Errors: 0 out of memory, 0 no buffers ARP cache: Total ARP entries in cache: 4 Dynamic: 3, Interface: 1, Standby: 0 Alias: 0, Static: 0 IP Packet drop count for node 0/0/CPU0: 1The following is sample output from the show arp traffic command with the location keyword and node-id argument:
RP/0/RSP0/CPU0:router# show arp traffic location 0/2/CPU0 ARP statistics: Recv: 0 requests, 1 replies Sent: 0 requests, 2 replies (0 proxy, 2 gratuitous) Resolve requests rcvd: 0 Resolve requests dropped: 0 Errors: 0 out of memory, 0 no buffers ARP cache: Total ARP entries in cache: 4 Dynamic: 1, Interface: 1, Static: 1 Alias: 1, Standby: 0 IP Packet drop count for node 0/2/CPU0: 1timers (DAGR)
To configure the Direct Attached Gateway Redundancy (DAGR) timers for sending ARP requests, use the timers command in DAGR peer interface configuration mode.
Syntax Description
query query-time
The value is a time (in seconds) between successive ARP requests being sent out to the virtual IP address, when the group is in the query state. The range of values is 1 to 10000.
standby standby-time
The value is a time (in seconds) between successive ARP requests being sent out to the virtual IP address, when the group is in the standby state. The range of values is 1 to 10000.
Command Default
The default for query-time is 1 second, and the default for standby-time is 20 seconds.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
When this function is applied, the DAGR group configuration is updated in the database.
The new timer values take effect the next time the timer is set. No immediate timer restarts are triggered on the basis of this event.
Task ID
Examples
The following example configures a DAGR group peer with a query time of 2 and a standby time of 40:
RP/0/RSP0/CPU0:router(config-if-dagr-peer)# timers query 2 standby 40 RP/0/RSP0/CPU0:router(config-if-dagr-peer)#Related Commands