proxy-arp

[tmesbah]

Hi,

After adding "no ip proxy-arp" on each interface of our Catalyst6509_SUP2-MSFC2 running on Hybrid mode CatOS 7.6.6 and IOS 12.1.20.E2, We lost some SUN server "Can not ping them" and we had to enable proxy arp on the interface of the router to make them pingeable.

Why do we have that. We don't use at all proxy-arp on our network.

Thanks

[Richard Burts · Accepted solution]

It sounds like there is some difference between the configuration of the SUN and the router about what is local on the wire. A workstation will ARP for addresses that it considers to be local and will forward to its gateway for addresses that it considers to be remote. A router with proxy ARP enabled will respond to an ARP request for an address that the router considers remote (if the router has a route to that destination address in its routing table). A router with proxy ARP disabled will respond to ARP requests only for addresses that it considers local and will ignore any ARP request for an address that it considers remote.

It sounds like the SUN is ARPing for an address that it considers to be local but that the router considers to be remote. In this case the router will respond to the SUN if proxy ARP is enabled and will not respond to the SUN if proxy ARP is disabled.

Can you verify how the SUN stations are configured (interface address and subnet mask will determine what it considers local) and how the router is configured? I suspect that you will find that there is some difference.

[tmesbah]

Thanks. Wrong mask on SUN servers