[CentOS] Routing w/ Two Interfaces

Sun Jun 18 19:42:31 UTC 2006
Fabian Arrotin <fabian.arrotin at arrfab.net>

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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