# Problem with ARP



## wrkilu (Sep 1, 2011)

Hi,

We have some border router with FreeBSD 8.2 x64. Recently we've looked strange thing. In some moment it can't ping some address IP, but when You delete his arp You can pinging this IP again. MAC of this IP is still the same. So.. what is going on ? All ARP table has about 700 MAC addresses.


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## Orum (Sep 3, 2011)

Are you sure the arp reply is being received my the machine making the request, and in a timely fashion?  If a few requests are dropped or time out, it might be negatively cached, preventing further arp requests for a period of time.

Check how long it takes and how reliable the replies are with tcpdump.


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## wrkilu (Sep 12, 2011)

I've checked by tcpdump. In some moment there isn't any arp reply indeed. But why router request for arp of some IP, when this arp is in table ?? strange.. 

Well, we think the reason is Dlink switch connected to the router. He didn't answer sometimes and that's why. 

thanks for help.


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