Linux Router

["Carlos Narváez" <crakup@gmail.com>]

 This is starting to frustrate me, because it should be much simpler
than it seems to be, and I feel like I'm missing something small and
obvious.

I have two private networks, we'll say 192.168.254.0/24 and
192.168.251.0/24. And I have a linux box in the middle with addresses
192.168.254.17 and 192.168.251.10:


+---------------+ . +----------------+
¦ 192.168.251.1 +---+ 192.168.251.10 ¦ . +----------------+
+---------------+ . ¦ 192.168.254.17 +---+ 192.168.254.16 ¦
. . . . . . . . . . +----------------+ . +----------------+


There is no NAT involved.. I just want the box in the middle to pass
traffic between the two networks. Here is what I have done:

- IP Forwarding has been enabled on the router via "echo 1 >
/proc/sys/net/ipv4/ip_forward"

- A route has been configured on 192.168.251.1 to point all traffic
for 192.168.254.0/24 to 192.168.251.10.

- A route has been configured on 192.168.254.16 to point all traffic
for 192.168.251.0/24 to 192.168.254.17.

- The command "iptables -I FORWARD -j ACCEPT" has been executed.

Now.. here's what happens. 192.168.251.10 can ping both interfaces on
the router. 192.168.254.16 can also ping both interfaces on the
router. However, 192.168.251.1 cannot ping 192.168.254.16, and
likewise, 192.168.254.16 cannot ping 192.168.251.1.

What have I forgotten?

-- 
Carlos Narváez
http://www.juegopixel.com