show ip arp not populating

[anthonykahwati]

Hello

I have a strange issue where a "show ip arp" only populates local addresses but does not populate with addresses learnt on interfaces in that VLAN. For example, vlan 10 has dozens of IP addresses attached on individual access ports. If I ping the broadcast, most of these addresses reply, but if I do "show ip arp" for the mac association, i get nothing.

I am using 3750x with 15.x software.

Can anyone shed any light on this at all? We have other 3750X switches with the same sort of config that are populting the output.

Thanks in advance

[Aaron Harrison]

Are you sure the VLAN10 interface is up and properly addressed? If it's not in the ARP cache then it may be routing via another L3 switch or route to reach the address. Try doing a traceroute to the IP you expect to see in ARP.

Aaron