Why I need " clear ip arp"

[mdavar]

Hi

I have few Nortel equipments connected to 3550, which in turn is connected to 3662 Router. It has been noticed that after some time (2-3 hours) in the router it doesn't show arp entry for a particular Nortel box. After clearing the arp cache it started showing the entry. The other boxes doesn't have this problem.

Any idea why this is happening.

I tried adding static arp entry, but the problem remains same.

Thanks in advance.

[DALE FRANCIS]

When you clear the ARP table on the Cisco, the Cisco will send out and ARP for each of the address's that were in the ARP cache.

Some boxes send out Gratutious ARP's to refresh local ARP cache's

[mdavar]

Is there anything in I can do with S/w or router to avoid giving this command again and again

[DALE FRANCIS]

You could bring down the ARP age timers, but do bear in mind that this wil cause a flood of ARP's every expirery time, altho on LAN this should not be an issue.

The other method might be to get the nortel to send out gratatious ARP's