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HSRP IP incorrect MAC

Hello all,

Our infrastructure has two sites, with two routers at each site. The routers are configured for HSRP with an IP address of .201. The physical IPs for these routers are .3 and .4. Yesterday we lost connectivity between the two sites. I was able to figure two workarounds without changing the default gateway on the PCs/servers. The first one was to add a static route to each machine, forcing it to use either real router IP (.3 and .4) to get to the other site. This works fine (but will be removed when permanent solution found). The other workaround is to add a static ARP entry on the PC, stating that the gateway address should resolve to the correct MAC address, which we established from the routers. This works for about 30 seconds, until the dynamic entry overwrites the static, with an incorrect MAC address.

The MAC that is being given to clients for the .201 address actually belongs to a server. No changes have been made to any equipment that could cause this. I would like to disable the NIC in the server temporarily to see if this helps, but I cannot down this server during working hours.

Has anybody seen anything like this before? Everything has been working fine for many months and nothing new introduced (at least nobody owning up to anything!)

Thanks a lot



Re: HSRP IP incorrect MAC

Check the server.

Even if everybody claims to have changed nothing, check if the server isn't configured as .201 (maybe someone made a typo?).

If the clients have the MAC of the server in their ARP table for .201, it means someone or rather something is sending ARP replies with this MAC address.

So check the server and if that is not it, I would sniff the network for ARP traffic.




Re: HSRP IP incorrect MAC

there is an interfac command ' standby use-bia' place this command on the interfaces that are configured for HSRP . This will force the routers to use the Mac address of the routers interface as its virtual mac. It has solved many HSRP issues for me , give it a shot

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