Re: ip forwarding

[Matt Zagrabelny <mzagrabe@d.umn.edu>]

On Tue, 2005-05-03 at 10:05 -0500, Matt Zagrabelny wrote:
> hello,
> 
> simple firewall problem:
> 
> 1 external nic (eth0)
> 1 internal nic (eth1)
> 
> i do not need to do any snat or masquerading, i am just looking to
> forward the traffic from the internal to the external.
> 
> so far:
> 
> # echo 1 > /proc/sys/net/ipv4/ip_forward
<snip>
> i have a client that is configured (via next hop routing) to have its
> traffic sent to the internal interface on the firewall box.
> tcpdump shows traffic getting to the internal interface, but not the
> external. any thoughts?

spoof protection on eth1 was the culprit.

echo 0 > /proc/sys/net/ipv4/eth1/rp_filter

-matt zagrabelny