CentOS - Aug 2009 - setup iptables to allow forwarding through eth1

I have a fresh installed CentOS 5.3 server which should route traffic
between two networks like this:

network A (Internet) -- eth0 (default gw) : server : eth1 -- network B (LAN)

I have set in sysctl.conf

net.ipv4.ip_forward = 1

and routing works fine like this. But when I switch on the iptables
service (with default setup, configured when installing the server),
routing stops working (or at least I cannot ping a server in network A
from network B).  I guess the firewall is stopping it, so I read

http://www.centos.org/docs/5/html/5.2/Deployment_Guide/s1-firewall-ipt-fwd.html

and issued the commands

# iptables -A FORWARD -i eth1 -j ACCEPT
# iptables -A FORWARD -o eth1 -j ACCEPT

but that did not help.

So I am asking: what is the correct iptables command to make forwarding work?

Regards,
Peter

Hi,

did you try:

iptables -I FORWARD 1 -i eth1 -j ACCEPT
iptables -I FORWARD 1 -o eth1 -j ACCEPT

??


On 30.8.2009, at 20:47, Peter Peltonen wrote:
> I have a fresh installed CentOS 5.3 server which should route traffic
> between two networks like this:
>
> network A (Internet) -- eth0 (default gw) : server : eth1 -- network  
> B (LAN)
>
> I have set in sysctl.conf
>
> net.ipv4.ip_forward = 1
>
> and routing works fine like this. But when I switch on the iptables
> service (with default setup, configured when installing the server),
> routing stops working (or at least I cannot ping a server in network A
> from network B).  I guess the firewall is stopping it, so I read
>
>
http://www.centos.org/docs/5/html/5.2/Deployment_Guide/s1-firewall-ipt-fwd.html
>
> and issued the commands
>
> # iptables -A FORWARD -i eth1 -j ACCEPT
> # iptables -A FORWARD -o eth1 -j ACCEPT
>
> but that did not help.
>
> So I am asking: what is the correct iptables command to make  
> forwarding work?
>
> Regards,
> Peter
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
Hodja Nasredin
nasredin at sutra.cz

Peter Peltonen wrote:
> I have a fresh installed CentOS 5.3 server which should route traffic
> between two networks like this:
>
> network A (Internet) -- eth0 (default gw) : server : eth1 -- network B
(LAN)
>
> I have set in sysctl.conf
>
> net.ipv4.ip_forward = 1
>
> and routing works fine like this. But when I switch on the iptables
> service (with default setup, configured when installing the server),
> routing stops working (or at least I cannot ping a server in network A
> from network B).  I guess the firewall is stopping it, so I read
>
>
http://www.centos.org/docs/5/html/5.2/Deployment_Guide/s1-firewall-ipt-fwd.html
>
> and issued the commands
>
> # iptables -A FORWARD -i eth1 -j ACCEPT
> # iptables -A FORWARD -o eth1 -j ACCEPT
>
> but that did not help.
>
> So I am asking: what is the correct iptables command to make forwarding
work?
>
> Regards,
> Peter
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
>   
my iptables like that:

    * iptables --table nat --append POSTROUTING --out-interface eth0 -j
      MASQUERADE
    * iptables --append FORWARD --in-interface eth1 -j ACCEPT

Regards

Firdaus
i'm come from indonesia. :)

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