[ILUG] Routing ppp and a null modem cable

[Paul Jakma]

On Tue, 17 Aug 2004, Bryan O'Donoghue wrote:

> Nope.
>
> box 1: lo:1 192.168.3.1, eth0 10.100.100.22
>    pppd -detach crtscts lock roxyarp 192.168.3.1:192.168.3.2 /dev/ttyS0 9600
>    more /proc/sys/net/ipv4/ip_forward == 1
>
> box 2: lo:1 192.168.3.2
> pppd -detach crtscts lock defaultroute 192.168.3.2:192.168.3.1 /dev/ttyS0 
> 9600
> route add -net default gw 192.168.3.1

presumably no default route existed previously?

what does 'ip route show 0/0' say?
what does 'ip ro get 10.100.100.22' say?

if you do:

 	ip route add 10.100.100.0/24 via 192.168.3.1

on box2 (3.1 is box1 right? and the 10.100.100.0/24 is correct prefix 
length?) does it work then?

> Pinging between the 192.168.3.x network works between the null 
> modem cable And box 2 definately can't ping 10.100.100.22
>
> Could this have something to do with the fact that on both machines 
> I'm using a second ip assigned to the loopback interface?

ip address show dev lo
ip address show dev ppp0

on both boxes..

it shouldnt make a difference, given that you must have things setup 
correctly as each box can ping the other end of the ppp link.

> Ordinarily, when ppp happens in the real world the IPs would be 
> assigned to interfaces called ppp(blah), I can't see why it would 
> make a difference, but, maybe pppd wants to route interfaces named 
> ppp(blah) only?

pppd doesnt route, and kernel automatically installs interface routes 
when pppd adds the addresses for it's link.

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
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