How do I make ARP cache age in 30 seconds?
Posted on 1998-09-09
How can I get an ARP cache to age in, say, 30 seconds. What I've got is the following:
A device with a given IP, say IP1, has a MAC address, say MAC1. During a short time interval, this device gets a new MAC address, MAC2. While IP1 has MAC1, it does a tftp transfer of a file from the tftp server. After IP1 gets MAC2, it tries to do another tftp, but tftp times out since the tftp server still sees MAC1 mapped to IP1.
I can manually intervene and do an "arp -d IP1" to clear the ARP entry, and then try the tftp transfer again with IP1+MAC2, which updates the ARP cache, and everything's fine.
Anyone have good ideas how to manage this without manual intervention?
What would happen if something were running on the tftp server to periodically clear the ARP entry for IP1, and this entry got cleared DURING a tftp transfer? Would it barf completely and stop, or just recover with a new ARP and be basically invisible?