At work we have a number of sites that connect to our media server. There are 3 remote sites in Minnesota and 1 in North Dakota.
The traffic travels through a VPN tunnel set up by Cisco routers.
I'll change the IP address a bit for the demonstration and linuxify this real world example.
172.28.100.0
Code:
# /etc/networks for this example
loopback 127.0.0.0
fargo 172.28.100.0
ada 172.28.101.0
fergus 172.28.102.0
perham 172.28.103.0
jamestown 172.28.104.0
The IP addresses use a Class B private IP range, subnetted so the netmask is 255.255.255.0. You are using a Class A private IP range. If you don't have close to 255 sites then having your addresses like 10.1.x.x and 10.2.x.x with a 255.255.0.0 netmask would be more typical, but I digress.
The routers have local addresses of 172.28.100.1, 172.28.101.1, 172.28.102.1, 172.28.103.1 and 172.28.104.1 respectively. So in Fargo, the default gateway is set to 172.28.100.1 and in Ada the default gateway is set to 172.28.101.1.
If this network also had internet access and a separate router, then these specific routes would need to be setup.
example for fargo:
Code:
route add -net 172.28.101.0 gw 172.28.100.1
route add -net 172.28.102.0 gw 172.28.100.1
route add -net 172.28.103.0 gw 172.28.100.1
route add -net 172.28.104.0 gw 172.28.100.1
Because I used an /etc/networks file, this would work.
Code:
route add -net ada gw 172.28.100.1
route add -net fergus gw 172.28.100.1
route add -net perham gw 172.28.100.1
route add -net jamestown gw 172.28.100.1
route add default gw <gateway-to-internet> dev <if-device>
Different distro's have different methods of setting up static routes. Also, the routes need to be configured for every host.
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Maybe I misunderstood your problem. Do you want to from India, connect to a UK computer on the Internet (outside the UK LAN), and have the traffic go through the tunnel to the UK and use the UK's gateway to the internet?
In that case I think you need a something like:
route add -host w.x.y.z gw 10.2.1.1
This will send the traffic through the VPN instead of out your local gateway in India. The VPN device may need to be configured so that it doesn't drop the w.x.y.z destination. It may be setup to only allow 10.1.1.1 <-> 10.2.1.1 traffic and drop everything else. That is to say, that the VPN routers may need a similar routing rules.
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If the w.x.y.z host is outside the UK LAN and on the internet, why not simply use the internet to make the connection?