VRF-Aware ARP Debug

Last Updated: October 15, 2012

The VRF-Aware ARP Debug feature provides debugging capability for Address Resolution Protocol (ARP) in a VPN routing and forwarding (VRF) environment. This feature is an enhancement to the ARP Rewrite feature.

Finding Feature Information

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Information About VRF-Aware ARP Debug

VRF-Aware ARP

You can enable debugging Address Resolution Protocol (ARP) on a particular VPN routing and forwarding (VRF) instance, a VRF on an interface, or both. Use the debug arp vrf vrf-name command to enable debugging ARP for a VRF. When you enable the debug arp vrf vrf-name command on an interface, the command displays only information about the VRF configured on the interface.


Note
The debug interface interface command must be enabled before the debug arp vrf vrf-name command is used on an interface.

How to Enable VRF-Aware ARP Debug

Enabling VRF-Aware ARP Debug

Perform this task to enable debug trace for Address Resolution Protocol (ARP) transactions to monitor the ARP subsystem.

Debug trace can be enabled for all IP ARP packet traffic, or it can be enabled for an individual type of ARP event, such as the following:

  • ARP entry events:
    • Any dynamic ARP entry event
    • Any interface ARP entry event
    • Any static ARP entry event
    • Any ARP entry subblock event
  • ARP table events:
    • ARP table operations (entry insertion, modification, or deletion)
    • ARP table timer events
    • ARP table database events (database read/write events)
  • ARP high availability (HA) events
  • ARP interface events:
    • ARP/Cisco Express Forwarding Adjacency interface transactions
    • ARP Application interface transactions
  • VPN routing and forwarding (VRF) or VRF on a particular interface

The amount of ARP debug information displayed is filtered according to the interface and access list specified by the debug list command.

SUMMARY STEPS

1.    enable

2.    debug list [list] [interface]

3.    debug arp [vrf vrf-name | global] [arp-entry-event | arp-table-event | ha | interface-interaction]

4.    show debugging

5.    no debug arp [vrf vrf-name | global] [arp-entry-event | arp-table-event | ha | interface-interaction]


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Device> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
debug list [list] [interface]


Example:

Device# debug list 1102 serial

 

(Optional) Enables the filtering of ARP debugging information (or debugging information for any of the other protocols supported by this command). The filtering is performed by using either or both of the following criteria:

  • To display debugging information for a specific interface rather than for all interfaces on a device, identify the interface by using the interface argument. If the interface needs to be configured, use the interface command.
  • To display information for a specific type of packet rather than for all packets, identify the packet details by using the list argument to identify an extended ACL. The ACL specifies a source MAC Ethernet address, the destination MAC Ethernet address, and arbitrary bytes in the packet. If the extended access list needs to be configured, use the access-list (extended-ibm) command.
 
Step 3
debug arp [vrf vrf-name | global] [arp-entry-event | arp-table-event | ha | interface-interaction]


Example:

Device# debug arp static

 

Enables debug trace for ARP packets.

  • Enables debug trace for one of the following specific types of ARP events:
    • VRF on an interface
    • ARP entry events
    • ARP table events
    • ARP HA events (on HA-capable platforms)
    • Interactions on an ARP interface
 
Step 4
show debugging


Example:

Device# show debugging

 

Lists the debugging options enabled on this device.

 
Step 5
no debug arp [vrf vrf-name | global] [arp-entry-event | arp-table-event | ha | interface-interaction]


Example:

Device# no debug arp static

 

(Optional) Disables debug trace for ARP packets.

  • This command disables debug trace for one of the following specific types of ARP events according to the specified keyword or argument:
    • VRF on an interface
    • ARP entry events
    • ARP table events
    • ARP HA events (on HA-capable platforms)
    • Interactions on an ARP interface
 

Configuration Examples for VRF-Aware ARP Debug

Example: VRF-Aware ARP

The following example shows that debugging information related to vpn1 on Ethernet interface 0/0 will be logged: 

Device> enable
Device# configure terminal
Device(config)# interface ethernet0/0
Device(config-if)# vrf forwarding vpn1
Device(config-if)# end
Device# debug arp vrf vpn1

Additional References for VRF-Aware ARP Debug

Related Documents

Related Topic Document Title

Cisco IOS commands

Cisco IOS Master Command List, All Releases

IP addressing commands

Cisco IOS IP Addressing Services Command Reference

IP addressing tasks

Configuring IPv4 Addresses

ARP configuration tasks

Configuring Address Resolution Protocol Options

ARP trace information

Monitoring and Maintaining ARP Information

Standards and RFCs

Standard/RFC Title

RFC 1812

Requirements for IP Version 4 Routers

Technical Assistance

Description Link

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http://www.cisco.com/cisco/web/support/index.html

Feature Information for VRF-Aware ARP Debug

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1 Feature Information for VRF-Aware ARP Debug
Feature Name Releases Feature Information

VRF-Aware ARP Debug

15.1(1)SY

The VRF-Aware ARP Debug feature provides debugging capability for ARP in an VRF environment. This feature is an enhancement to the ARP Rewrite feature.

The following command was introduced or modified: debug arp.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2012 Cisco Systems, Inc. All rights reserved.