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How long the cisco 7513 will update its arp table?

There are two (2) AS400 machine in my bridge network. These two AS400 machine are up at the same time using different IP addresses,

When I intentionally down the first AS400 machine and replace its current ip address to the second AS400 I could not ping the IP address, However when I check the arp table of my core router (also a network gateway) I noticed that the ip address and the down as400 mac address still there.

Meanwhile the switch on the other side of ny bridge network updates its arp table immediately, the ip address is there as well as the mac address of the new machine. there are now two (2) mac address using a single IP in my bridge network (one mac address is in my core router 7513 arp table and the other mac address that use the same ip is in the switch arp table). The problem is the active machine do not respond when i ping...

It took an hour for the cisco 7513 to automatically refresh its arp table and the ip address previously I use in down AS400 is now up. The sh arp command displays that the ip address is now belongs to the second AS400 machine.

Since I’m convinced that this scenario is not normal to my network, I would like to know a work around to speed up the Cisco 7513 arp table refresh. Any idea?

1 REPLY
Bronze

Re: How long the cisco 7513 will update its arp table?

Use the "arp timeout" command to define how long an arp entry is cached: http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipras_r/1rfipadr.htm#1017519

Be aware that lowering the timeout value will result in an increase in ARP traffic on your network.

Alternatively, use "clear arp-cache" to manually clear the (entire!) arp cache when you encounter this problem: http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipras_r/1rfipadr.htm#1017564

hth

Herbert

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