[Asterisk-Users] OT: Linux routing with T100P problems

[Dorn Hetzel]

On Tue, Dec 28, 2004 at 11:18:42PM -0600, Matthew Boehm wrote:
> Hey gang,
>  I was successful in recompiling my 2.4.20 kernel to support HDLC. I was
> successful in hooking up our T1 line into the zap card. I was successful in
> being able to ping equipment on the other end of the T1. I was unsuccessful
> in pinging the outside world from the other end of the T1.
> 
> I've attached a cheezy image of the network. Here is the routing table:
> 
> [root at asterisk root]# route
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> 10.0.5.2           *             255.255.255.255 UH    0         0        0
> hdlc0
> 10.0.0.0           *               255.255.255.0   U       0         0
> 0    eth1
> 10.0.3.0           *               255.255.255.0   U       0         0
> 0    eth1
> 65.78.109.0     *               255.255.255.0   U       0         0        0
> eth0
> 127.0.0.0         *               255.0.0.0           U       0         0
> 0    lo
> default       65.78.109.2     0.0.0.0               UG    0         0
> 0    eth0
> 
> There are 2 NICs (10.0.3.10, 65.78.109.10) and 1 T100P (10.0.5.1) on this
> box.
> 
> Like I said above, from this machine I can ping everything in every attached
> network and the outside world. For some reason, I cannot ping the outside
> world if I am comming from the 10.0.0.* network on the diagram. From that
> network, I can ping 10.0.5.1 (this box) but nothing else.
> 
> I'm a little stumped. My iptables are completly empty. If this is waaayyy
> off topic, please contact me off list. But I figured since it was related to
> the T100P it might be relevant.
> 
> What can I use to find out why packets destined for the outside world (via
> 65.78.109.2) are not being routed?
>

Since 10.x.x.x is RFC1918 private space which no real-world addresses
will/can reply to, you need to use masquerading (NAT) so that all of 
the packets to the "outside world" appear to come from a public
routable address on the outside of your gateway box.

-Dorn