We've went through and disabled proxy-arp on all of our server farm vlans to ensure the servers are accurately configured with the correct gateway and mask information. However on one vlan we had a primary subnet and two secondaries with proxy-arp disabled for the vlan. There were no apparent problems with this configuration. We then migrated one of the secondary subnets to its own vlan, in which we also disabled proxy-arp. When we did this, several servers for that subnet went down. Turns out their default gateways were misconfigured. Enabling proxy-arp put a band-aid over the problem. I guess I'm wondering why this wasn't an issue when the subnet was secondary with proxy-arp disabled. Does disabling proxy-arp only apply to the primary subnet?
Re: How does proxy-arp work with secondary addresses?
Disabling proxy arp is done on the interface, and should cover secondary interfaces. It is likely the misconfigured default gateways were using one of the other logical interfaces which resided on that physical interface.
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