[CentOS] proxy arp on CentOS 5?

[Florin Andrei]

Florin Andrei wrote:
> Anybody implemented a working proxy ARP with CentOS 5?
> 
> I am trying to implement DNAT on a dual-homed firewall (servers behind 
> firewall are on private IPs) and that requires proxy ARP. I've tried 
> several different methods but nothing seems to work.

I figured it out. I actually tested the idea yesterday, but it failed 
because one of the test machines was not configured properly.

To make proxy ARP work with DNAT, an IP alias must be created on the 
external interface, with the public IP address of the machine behind the 
firewall.

ip address add XXX.YYY.ZZZ.KKK dev eth0

where XXX.YYY... is the public IP address that corresponds to the 
private IP address of a server behind the firewall.

It's not even necessary to play with proxy_arp in /proc. Just the IP 
alias and DNAT.

-- 
Florin Andrei

http://florin.myip.org/