[CentOS] Centos firewall/router issue

Thu Feb 22 21:19:37 UTC 2007
Will McDonald <wmcdonald at gmail.com>

On 22/02/07, Dustin Krysak <d.k.emaillists at gmail.com> wrote:
> Good day everyone. Today has been "one of those..." days. So I have a
> feeling this is just a brain lapse here.
>
> At any rate, I am setting up a firewall/router using centos 4.4
> (minimal install, yummed up to date).
>
> It "seems" like the traffic is not being forwarded, but I have run the
> following command to confirm the ip forwarding is on:
>
> # cat /proc/sys/net/ipv4/ip_forward
>
> And I do in fact have a "1" in there.

Is the firewall NATing outbound traffic? If you can, can you stop
iptables and just see if simple IP routing is working as expected? If
you tcpdump all traffic for a little used port on both interfaces,
then try telneting out to that port on an external host, does the
packet appear on the external interface? What do the routing tables
look like?

Just a few suggestions.

Will.