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TOPIC: Proxy ARP

Proxy ARP 12 years 1 week ago #5078

  • TheBishop
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A problem has appeared on one of my LANs which presents itself as a duplicate IP address. However there definitely isn't a real duplicate IP out there. What happens is on a Windows PC I get the 'duplicate IP address detected' message and on a Solaris box the more helpful kernel warning 'Hardware address xx:xx:xx:xx:xx:xx trying to be our address yy:yy:yy:yy:yy:yy'. The network runs fine for ages, then suddenly the problem hits and everything goes nuts for either seconds or a few minutes. Then it clears on its own and all is fine again. There are several devices on the LAN that do proxy ARP, and I have a feeling something is messing up ARP and responding with incorrect MAC addresses to ARP requests. So...

1) Can anyone give me a potted explanation of proxy ARP and how it might relate to my problem (I understand the ARP mechanism well)

2) Anybody seen anything like this before??!?

Thanks!
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Proxy ARP 12 years 1 week ago #5083

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Thanks for the deluge of replies on this one :lol: :lol:
On further investigation I interpreted the error message (see previous post) from the Solaris box wrongly. It actually reads 'Hardware address <correct MAC address of this server> trying to be our address <corect IP address of this server>'. So this machine is complaining that it is having an IP address conflict with itself! How can a Solaris box be getting confused about its own MAC address???
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Re: Proxy ARP 12 years 1 week ago #5095

  • Chris
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No that certainly is a very weird problem and one I have never come across. I'm not sure what to suggest at this point, but have you tried a search on google ?

If you have and progress, let us know!
Chris Partsenidis.
Founder & Editor-in-Chief
www.Firewall.cx
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Re: Proxy ARP 11 years 9 months ago #6086

You have probably solved the problem, but maybe someone has set his box to have the same MAC+IP yours has, thus creating the hilarious stuation.
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Problem 11 years 9 months ago #6090

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No, it wasn't that. And I didn't really solve it either. It happened on and off for a couple of weeks then just disappeared on its own. And there was no device replacement or change etc that might have been responsible. I remain mystified
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Re: Proxy ARP 11 years 9 months ago #6107

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Don't you just hate these problems that come and go without reason?

I'm currently trying to figure out why we are experiencing jittering problems with our IP Phone network and while researching, I've found that some switches are showing unicast traffic across their ports which shouldn't be seen!

What's this world coming to ? :shock:
Chris Partsenidis.
Founder & Editor-in-Chief
www.Firewall.cx
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