How do I view ARP entries?
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ARP CommandsThis 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.
arpTo 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
Command DefaultNo entries are permanently installed in the ARP cache. Command ModesGlobal configuration Command History
Usage GuidelinesTo 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 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
ExamplesThe 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 arpa Related Commands
arp dagrTo configure Direct Attached Gateway Redundancy (DAGR), use the arp dagr command in interface configuration mode. Syntax DescriptionThis command has no arguments or keywords.
Command ModesInterface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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
arp purge-delayTo 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. arp purge-delay value no arp purge-delay value Syntax Description
Command DefaultDefault value is off. Command ModesInterface configuration Command History
Usage GuidelinesTo 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. 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
ExamplesThe following is an example of setting the purge delay to 50 seconds: 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 purge-delay 50 arp timeoutTo 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. arp timeout seconds no arp timeout seconds Syntax Description
Command DefaultEntries remain in the ARP cache for 14,400 seconds (4 hours). Command ModesInterface configuration Command History
Usage GuidelinesTo 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. 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 04:00:00 Task ID
ExamplesThe 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 3600 Related Commands
clear arp-cacheTo 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. clear arp-cache { traffic type interface-path-id | location node-id } Syntax Description
Command DefaultNo default behavior or values Command History
Usage GuidelinesTo 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 issued without keywords or arguments, the clear arp-cache command clears all entries in the ARP cache. Task ID
ExamplesThe 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/CPU0
The 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/CPU0
Related Commands
peer (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 ModesDAGR interface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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)# Related Commands
priority-timeoutTo 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
Command DefaultDefault for time is 20 seconds. Command ModesDAGR peer interface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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-arpTo 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. Syntax DescriptionThis command has no arguments or keywords. Command DefaultProxy ARP is disabled on all interfaces. Command ModesInterface configuration Command History
Usage GuidelinesTo 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 proxy ARP is disabled, the networking device responds to ARP requests received on an interface only if one of the following conditions is met:
When proxy ARP is enabled, the networking device also responds to ARP requests that meet all of the following conditions:
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
ExamplesThe following example shows how to enable proxy ARP on MgmtEth interface 0/RP1/CPU0/0: RP/0/RSP0/CPU0:router#(config)# interface MgmtEth 0/RP1/CPU0/0 RP/0/RSP0/CPU0:router#(config-if)# proxy-arp route distanceTo configure route distance for a given Direct Attached Gateway Redundancy (DAGR) group, use the route distance command in DAGR peer interface configuration mode. route distance normal normal-distance priority priority-distance Syntax Description
Command DefaultDefault for normal-distance default is 150 and the default for priority-distance is 5. Command ModesDAGR peer interface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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 metricTo 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. route metric normal normal-metric priority priority-metric Syntax Description
Command DefaultThe default for normal-metric is 100, and the default for priority-metric is 90. Command ModesDAGR peer interface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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 arpTo display the Address Resolution Protocol (ARP) , enter the show arp command in EXEC mode. show arp vrf vrf-name [ip-address | hardware-address | interface-path-id] location node-id Syntax Description
Command DefaultThe active RSP is the default location. Command History
Usage GuidelinesTo 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 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
ExamplesThe 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/CPU0/0 The 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/CPU0/0
The 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 GigabitEthernet2/0/1/2
The 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.
Related Commands
show arp dagrTo display the operational state of all Direct Attached Gateway Redundancy (DAGR) groups, use the show arp dagr command in EXEC mode. show arp dagr [ interface [IP-address] ] Syntax Description
Command History
Usage GuidelinesTo 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
ExamplesThe following example shows the current operational state of the DAGR groups: RP/0/RSP0/CPU0:router# show arp dagr
--------------------------------------------------------------------------------
0/1/CPU0
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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 None
Related Commands
show arp trafficTo display Address Resolution Protocol (ARP) traffic statistics, enter the show arp traffic command in EXEC mode. show arp traffic [ vrf vrf-name ] [interface-path-id] [ location node-id ] Syntax Description
Command History
Usage GuidelinesTo 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
ExamplesThe 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: 1
The 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: 1
Related Commands
timers (DAGR)To configure the Direct Attached Gateway Redundancy (DAGR) timers for sending ARP requests, use the timers command in DAGR peer interface configuration mode. timers query query-time standby standby-time Syntax Description
Command DefaultThe default for query-time is 1 second, and the default for standby-time is 20 seconds. Command ModesDAGR peer interface configuration Command History
Usage GuidelinesTo 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
ExamplesThe 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
Where can you find the arp entries?An Address Resolution Protocol (ARP) entry allows an interface to communicate with another interface even if they are not in the same multicast group. An ARP entry can be created manually using the arp -t ib command. To display all ARP entries, run the$ arp -t ib -a command.
What are the entries in your arp table?Each switch has an ARP (Address Resolution Protocol) table to store the IP addresses and MAC addresses of the network devices. The ARP table is used to determine the destination MAC addresses of the network nodes, as well as the VLANs and ports from where the nodes are reached.
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