Sometimes when you are changing out equipment it takes a long time until the new equipment will reply on ICMP. This is often because the layer 3 / 2 mapping information (arp) is old. The result of this is that the frames will have the wrong destination MAC address, and never even receive the frames.
To clear out an IP address from the ARP cache just issue:
clear ip arp <ip address>
This will cause the IP address / MAC mapping to get booted from the device, and it will then do the process of relearning it.
Tags: arp
Follow me on twitter