IP routing should be turned off by default. You will also need to edit your /etc/sysctl.conf file so that the line that reads:
net.ipv4.ip_forward=0 reads net.ipv4.ip_forward=1
This will enable IP forwarding on all interfaces; if you want to enable it on just one interface then you will need to remove the previously stated line and add a line in /etc/sysctl.conf that reads:
net.ipv4.conf.<interface>.forwarding=1 ## Replacing interface with the appropriate interface (ex. eth0).
I also want to remind you that enabling ip routing on any interface is a security risk, so be warned.
Also look out for the response from my friend Eric Davis, he is explicitly looking into this just for you; so if you still have issues maybe he can provide some insight.
On 6/18/06,
Fabian Arrotin <fabian.arrotin@arrfab.net> wrote:
Hummh, maybe the following question may seem silly, but have you enabled
ip routing on your CentOS box ?
What's the result of cat /proc/sys/net/ipv4/ip_forward ?
If you have enabled ip routing , maybe have a look at your firewall
rules to be sure that you don't drop any packets ...
On Sun, 2006-06-18 at 15:06 -0400, Michael B Allen wrote:
> I have two interfaces on a centos machine with IPs 192.168.2.15
and
> 192.168.3.15. The routing table is:
>
> # route
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 192.168.3.0 * 255.255.255.0 U 0 0 0 eth1
> 192.168.2.0 *
255.255.255.0 U 0 0 0 eth0
> 169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
> default 192.168.2.1 0.0.0.0 UG 0 0 0 eth0
>
> The gateway 192.168.2.1 is a wireless router on which I have a static
> route for 192.168.3.0/24 to 192.168.2.15.
>
> The problem is I cannot communicate between these networks. If I ping
> from a machine on
192.168.2.0 to a machine on 192.168.3.0 it never makes
> it. If I run tcpdump -i eth0 on the machine with two nics, I can see the
> ICMP packets coming in so I know the static route on the wireless router
> is working. If I run tcpdump -i eth1 I cannot see the ICMP packets. So the
> routing is wrong. I can successfully ping the machine on the 192.168.3.0
> network from the machine with two interfaces.
>
> I would think that a packet sent from 192.168.2.100 for 192.168.3.128
> would go to the gateway, get sent to
192.168.2.15 which it would go
> though the above listed routing table, match 192.168.3.0 and get sent
> to eth1. What am I doing wrong?
>
> Mike
>
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Thx
Joshua Gimer