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ARP Requests

I have been troubleshooting a problem that happens every so often on some of my vlans. I have 2 6509's configured with multiple vlans using an msfc. I have been recieve input buffer drops. When investigating this problem with my sniffer, I notices that when the buffer fills up it's due to a large number of arp request sent from them router to every workstation on that segment. What would make the router all at once start senting arp requests? I have the ARP table (MSFC)set to 4 hours , the cam table(6509) set to 5 min and the mac table(3548) set to 5 min agingtime. Normal ARP request from a workstation to the router are replied with the gateways mac address, I want to know if this is normal also?


Re: ARP Requests

ARP requests are sent to every station until it finds a match, so any time the router gets a request for an IP not in the cache, it will flood out ARP packets until it gets a response. Also, if the gateway will respond with its mac address to any IP on another segment, and the router does the packet rewrites as it sends data on to the destination.

Community Member

Re: ARP Requests


I'm not sure if I understood well your problem, but anyway... I think that you can avoid that behaviour by disabling proxy-arp on the MSFC's interfaces.

Hope this helps.


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