Re: bridge between ppp and ethernet - 1 IP address and assign it to another host

[Remco van Mook <remco@slashme.org>]

I've been toying with the suggestion to do something with routing table 0 to
accomplish this, and I can report it works, standard 2.6.10 kernel. Here's how
I did it:

Assuming a linux system, connected to a local network 172.16.0.0/24, own
address 172.16.0.13, 'ppp' ip address to be assigned to a system that has
ip address 172.16.0.4

On the box that establishes the PPP connection:
1) establish ppp connection, get IP address, say 192.168.0.2
2) ip route del local 192.168.0.2
3) ip route add 192.168.0.2 via 172.16.0.4

On the other box, 172.16.0.4:

1) ip addr add 192.168.0.2 dev eth0
2) ip route add 0/0 via 172.16.0.13

I didn't bother assigning the IP address for the other box dynamically; that
might still pose a challenge - outside the scope of netdev IMHO.

Optionally you might want to SNAT outbound traffic on the PPP interface to
enforce the correct IP address. Of course the solution doesn't actually
'bridge' the traffic, you get another visible hop, but the effect is almost
the same.

Kind regards,

Remco van Mook