[CentOS] Problem with CentOS server: am I running a firewall?

[Filipe Brandenburger]

On Tue, Apr 15, 2008 at 5:33 PM, Timothy Murphy <gayleard at eircom.net> wrote:
>  Unfortunately, I have not been able to set it up
>  to allow local machines to access the internet.

Did you enable routing? The output of "cat
/proc/sys/net/ipv4/ip_forward" must be 1, otherwise the server won't
route packets between networks. In some cases (depending on your
Internet modem/router) it's possible that you'll need to configure the
server to do NAT as well.

You can see the firewall rules with the command "iptables -nL". You
can delete all rules by running "iptables -F" (beware, your server
will be unprotected if you do that).

If you give more details about your network topology, it would be
easier to help you. You may also look at the contents of
/etc/sysctl.conf and /etc/sysconfig/iptables on your old server,
probably the routing, NAT and firewalling configuration of that server
is there.

HTH,
Filipe