Hello,

We discovered a strange network problem.

It seems we have a broken NIC that pronounces arp entries.
If a specific private ip address is pinged, then it seems two NICs answer the request. One answers correctly with the correct MAC address, and then there's a second answer with a wrong MAC address.

The strange thing is that all our linux servers and PCs only learn the correct address. But the windows PCs (all of them) learn the wrong address and consequently cannot communicate with the ip address.

So this is partially a windows problem.

But why doesn't linux suffer from the same problem?
It should also see the two answers. Somehow it decides to use the right one - it seems.

How can I investigate further what's going on?
I know which device is sending the wrong arp answers.

It seems this is done from time to time only - not each time.

Any ideas what to do about this strange problem?

Thank you very much,

Regards

Something to do with arp cache handling, possibly Linux keeps the first answer it received but Windows keeps the last? Not Sure.

Swap out the NIC, see if it does the same thing?
Not sure what else to suggest other than having a close look at the OS or device config to see if there is any reason why it might be doing this. Some kind of proxy response?

What is the misbehaving device btw?