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New Member

Constant ARP requests

Hi,

I have a cisco 4500 with IOS 11.2. Two out of five ethernet interfaces are putting out constant and sequential ARP requests for every address on their subnet. The other three interfaces don't do this. ANy idea what's going on? Thanks.

6 REPLIES
New Member

Re: Constant ARP requests

Have you checked the timing on when they flush their arp cache?

New Member

Re: Constant ARP requests

arp timeout is 4 hours, same as the others.

Bronze

Re: Constant ARP requests

This is commonly the result of hosts on the network being infected with worms which scan the local subnet for other hosts to infect.

New Member

Re: Constant ARP requests

Yes, I have seen that. According to etherpeek, though, these requests are originating at the router interface, not at any host.

Bronze

Re: Constant ARP requests

It could be a remote host (i.e., on another subnet) scanning the subnets in question then. In this case it's the router itself that would ARP for the destination addresses.

Cisco Employee

Re: Constant ARP requests

Apply the access-list to check to see if you are hit by blaster virus

http://www.cisco.com/warp/public/707/cisco-sn-20030814-blaster.shtml

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