[plug] Routing problem with PPTP VPN

[Paul Dean]

On Sat, 9 Feb 2002, Jeremy Malcolm wrote:

> Just wanting to get one or two fresh pairs of eyes to look at this problem,
> because I'm out of ideas for now.
> 
>         .--[]-[]-[] 192.168.0.0/24 LAN   .--[]-[]-[] 192.168.1.0/24 LAN
>         |                                |
>    .----------. ppp0 .--------. ppp0 .-------.      
> .--|Kalgoorlie|-----( Internet )-----| Perth |--.
> |  `----------'      `--------'      `-------'  |
> |  192.168.0.1                      192.168.0.40|
> `------------------ PPTP VPN -------------------'
>                    (/dev/ppp1)
> 
> Perth's gateway machine can ping Kalgoorlie fine over the VPN and vice versa. 
> All of the machines on Perth's network can ping the Internet fine over IP
> Masquerading.  But, none of the machines on Perth's network apart from the
> gateway can ping Kalgoorlie over the VPN.
> 
> The routing table looks thus (irrelevant fields snipped):
> 
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Iface
> 192.168.0.1     *               255.255.255.255 UH    ppp1
> terminus.net.au *               255.255.255.255 UH    ppp0
> 192.168.1.0     *               255.255.255.0   U     eth0
> 192.168.0.0     192.168.0.1     255.255.255.0   UG    ppp1
> default         terminus.net.au 0.0.0.0         UG    ppp0
> 
You need to change you ppp1 device IP's to it own network, you can't
route over an existing broadcast address, well you could but it will be
a one way afair.
This looks like Perth's route table? yes?
If it is where is the route for 192.168.0.40 --> space....so your
traffic disappears.

Your internal LAN IP is fine I would suggest using 172.16.0.1 for Perth
ppp1 and 172.16.0.2 for Kal, this will separate the networks but
maintain the netmask/broadcast addresses.

Then you add to your route table the addresses and GW retrospectively.

> Firewalling problems have been ruled out.
> 
> TIA
> 
> 

-- 
Paul Dean.
Canning College IT Support.