Alcatel Carrier Internetworking Solutions 6624 User Manual

ARP Protocol Failure

Troubleshooting ARP

page 11-2

OmniSwitch Troubleshooting Guide

If device A is not able to communicate with device B, it could be a result of ARP resolution failure. To 
troubleshoot ARP the first reference point is to make sure that the MAC address of device A and device B 
are learned on the right port and in correct VLAN.

Use the following command syntax:

show mac-address-table slot number

In our case we have a device connected in slot 16, so the command to verify the MAC address is as 
follows:

-> show mac-address-table slot 16
Legend: Mac Address: * = address not valid

   Vlan      Mac Address          Type       Protocol    Operation    Interface
------+-------------------+--------------+-----------+------------+-----------
10 08:00:20:a8:f0:8a learned       10800 bridging      16/2 
Total number of Valid MAC addresses above = 1

This command displays that MAC Address 08:00:20:a8:f0:8a, belonging to Device A, is learned on port 
16/2 and in VLAN 10.

A more comprehensive look for all the MAC addresses learned by the switch can be done by using the 
show mac-address-table command. For example:

-> show mac-address-table

Now, verify that the gateway defined in device A points towards the correct IP address. In our case, the 
gateway of device A is defined as 10.10.42.1.

 

 Workstation: A