PPPD - SSH - VPN Routing issues.

[steve.milner]

I've been having a spot of bother with some of our friends from abroad - OK I'm uk based and could easily be accused of xenophobia.

I was out in the Far East recently on company business and was tasked with getting the existing and inplace VPN working between our UK head offce and Far Eastern Office.

It was a simple routing issue and hey presto - the VPN was established.

Now ite seems that the relevant Government Officials have now blocked port 500 (Open VPN) and our router there (Billion BiGuard30) will not allow a differing port to be used and it seems that the UK end (IPCop Linux Distro) can't change the port either - or so I'v ebeen informed.

Anyway not to be beaten it seems that you can use a little unix to get round this. Using pppd and ssh it is possible to set up a VPN using linux boxes. I used this recipie here: http://tldp.org/HOWTO/ppp-ssh/index.html to demonstrate a proof of concept bteween my laptop at work and my home PC.

I can reliably bring up the ppp0 intrefaces at both ends and can hapily ping between the two ends.

Using pppd I have set up the interface as :

Laptop : 192.168.254.1
Home PC : 192.168.254.254

Laptop LAN - 172.31.0.0/16
Laptop LAN IP - 172.31.3.73
Home LAN - 10.200.1.0/24
Home PC LAN IP 10..200.1.249

I have my routing tables set as follows:
Laptop:
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.254.254 * 255.255.255.255 UH 0 0 0 ppp0
10.200.1.0 192.168.254.254 255.255.255.0 UG 0 0 0 ppp0
172.31.0.0 * 255.255.0.0 U 0 0 0 eth0
default xxx.xxx.xxx 0.0.0.0 UG 0 0 0 eth0

Home PC
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.254.1 * 255.255.255.255 UH 0 0 0 ppp0
10.200.1.0 * 255.255.255.0 U 0 0 0 eth0
172.31.0.0 192.168.254.1 255.255.0.0 UG 0 0 0 ppp0
default xxx.xxx.xxx 0.0.0.0 UG 0 0 0 eth0

OK This is the bit that needs careful examination:
From my laptop I can ping 10.200.1.249
From my home PC I can ping 172.31.3.73
From my Home TV (10.200.1.250) with an added route I can ping 172.31.3.73
From a colleagues PC (172.31.3.252) with an added route I can ping 10.200.1.249
From my Home TV (10.200.1.250) with added routes I can ping 172.31.3.252
From a colleagues PC (172.31.3.252) with added routes I can ping 10.200.1.250
From my laptop I can not ping 10.200.1.250
from my home PC can not ping 172.31.3.252

I do not uderstand why the last 2 pings fail (Other networking between these two points fails as well)

If anyone here can shed some light on these results I would be greatful.

Regards,
Steve