ARP issues.

[lennarth_selander]

I have a setup with 3 Windows 2003 servers connected to a Catalyst 3560.

The Catalyst has an uplink to an ASA5510.

I have an issue with that the servers every now and then cannot communicate with each other.

Communication to and from host behing the ASA works fine.

In the servers and catalyst I can se the ASA interface mac-address in the ARP table when it's not working. This happens when i flush servers ARP chance.

For now it working since I added the no proxyarp on that interface in the ASA.

I'm not sure if that is how it should be.

How can I trouble shoot this?

Thanks

[andrew.prince]

below is a heads up on proxy arp - explains all.

Do you have the servers pointing to the ASA as the default gateway?

[lennarth_selander]

Yes, the servers has the ASA as the default gateway.

[andrew.prince]

With the link this time!

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094adb.shtml

[lennarth_selander]

Thanks for the link.

But that my problem is that the ASA did send an reply back to a host on the segment the broadcast came from.

The servers should receive a reply direct from the server which has the IP address when they are on the same segment.

To me it looks like there are some issues with the servers or that the ASA is doing something wrong.

[andrew.prince]

OK - an arp is a broadcast from the MAC address of the source machine to the ethernet broadcast address of the LAn segement - typically something like "who has x.x.x.x tell x.x.x.x"

So typically when a device on the LAN wants to talk to the server and does not have an ARP entry for it, it will broadcast out on the LAN segement and the server should recevie and say "thats me" and send back an arp reply saying something like "x.x.x.x is at aa:bb:cc:dd:ee:ff"

The ASA should not have to get involved unless it has proxy arp enabled - and the machine does not have a default gateway configured?

HTH>

[fashour]

I am having the same problem.