Best practice removal of "Proxy Arp"

Unanswered Question
Dec 16th, 2008

I wanted to remove the "proxy arp" off the outside and DMZs.. would this create issues?

I have this problem too.
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Jon Marshall Tue, 12/16/2008 - 08:12

It depends on whether or not you have "static" statements in your config. ie.

static (inside,outside) 217.22.12.66 192.168.5.1 netmask 255.255.255.255

this tells the ASA that any traffic received on the outside interface for 217.22.12.66 should be translated to 192.168.5.1 and forwarded to the inside. If you disable proxy-arp on the outside interface then the above would stop working because the ASA can no longer respond for arp's to the public IP address.

Jon

sct0321 Tue, 12/16/2008 - 09:52

ok... so since I'm using static commands I shouldnt have any issue with the outside "proxy arp removal".?

Jon Marshall Tue, 12/16/2008 - 11:08

Apologies if i didn't explain correctly. If you have any static commands that reference either the outside or dmz interfaces then there will be an issue removing. You can only remove it where the firewall does not have to respond to an arp for that IP address. The interfaces you are concerned with are the second one in the static command ie.

static (inside,outside) ....

removing proxy-arp on the outside would cause problem

static (outside,inside) ....

wouldn't cause a problem removing proxy-arp on outside

Usually the outside interface is the one where you need proxy-arp.

Jon

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