[techtalk] ip masquerading

Brian Sweeney bsweeney at imagedog.com
Fri Jan 19 14:27:13 EST 2001

'Lo all-

I seem to be having some trouble using a virtual interface for an ip
masquerading rule using ipchains in RHL6.2.  here's the line:

ipchains -A forward -i <public interface> -s -j MASQ

On the box, I've got 2 nics...eth0 and eth1.  I've also got a virtual
interface, eth0:1, bound to an IP in the same subnet (obviously) as eth0.
When I specify eth0 in the above line for the public interface, everything
works fine.  But if I specify eth0:1, it simply ceases to even forward the
packet, never mind masquerade it.  A tcpdump of a ping from an internal
client to an external client shows the request coming in on the internal
interface, and nothing coming out on the external.  Any ideas?  The virtual
interface does seem to work in every other respect; I can ping it, ssh to
it, etc.

Thanks in advance,

Brian J. Sweeney
"I want to know God's thoughts ... the rest are details." -Albert Einstein
Systems Admin, imagedog
bsweeney at imagedog.com

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