[CentOS] Building a basic router with two nic's

[Marko A. Jennings]

On Wed, August 16, 2006 5:53 pm, kai wrote:
> Chris Mauritz wrote:
>> By the way, if you just want to set up a simple bridge between two
>> networks, I remember reading an article in Linux Journal last year
>> sometime (fires up Google....here it is):
>>
>> http://www.linuxjournal.com/article/8172
> Thank you for the link to the article, yes that's the funksion I'm
> looking for.
> But then, maybe a lame question,
> How to set up a router that just forward packets to next hop?
>
> I have googled my self blue without anything.
>
> Yes I have 2 nic,s on the same machine and using a crossed cable, so
> hooking up on each side works fine.
>
> I need to hook up equipment on the one side to monitor packets used, and
> also I would like to use the CentOS as a router towards the wan with my
> new sangoma s518 card, but if I can't route between two simple nic's I
> feel stuck.
>
> Thanks

As root, you can enable ip forwarding between interfaces by executing

  echo 1 > /proc/sys/net/ipv4/ip_forward

To make it permanent, set net.ipv4.ip_forward in /etc/sysctl.conf to "1":

  net.ipv4.ip_forward = 1

Marko