One lan on two ADSL modems connected to the same ISP

Question

We have two routers connected to the same ISP, both are connected to the ISP through ADSL. Computer a is connected to router A, and b is connected to router B.

tracert from a to B is 3 hops:

1. a to A
2. A to ISP's default gateway
3. ISP's default gateway to B

This is how the network looks like:

                                  ---Internet---
            _______________        ______|_______        _______________  
           |               |      |              |      |               |
a-Ethernet-| ADSL Router A |-ADSL-|     ISP      |-ADSL-| ADSL Router B |-Ethernet-b
           |_______________|      |______________|      |_______________|

• A's internal netowrk uses 192.168.168.x (subnet mask 255.255.255.0)
• B's internal network uses 192.168.1.x (subnet mask 255.255.255.0)
• ISP's internal network uses 55.65.x.x (subnet mask is 255.255.0.0)
• ISP's Default Gateway IP address is: 98.170.201.1
• ISP doesn't isolate the clients (A and B can 'send/receive' data 'to/from' each other)
• Both a and b are windows machines
• A and B are in different locations

I hope this is informative enough, tell me if it lacks any information.

I want to put a and b into the same LAN (virtually - as if they were in a real LAN. I don't have access to ISP's configuration as I am a client. It's for Gaming and file transfer purposes, and it should not involve the internet as using ISP's internal network is cheaper, faster and more reliable than using the internet. That's the whole idea behind it.

Answer 1

You can't put A and B into the same LAN, because you'd need to manipulate what happens on the ISP's routers do that, and even if you were asking your ISP nicely, they won't do that.

However, you can connect A's LAN with B's LAN via a tunnel, so you can make it look like they are in the same LAN (when in fact they aren't).

There are various ways to set that up (on A and B, on the routers if you have access, on a third machine in the local LAN; not using encryption or using encryption), so the best way to do that depends on your circumstances, the OS's you are using, and your other requirements.

One way to do it is to install an OpenVPN client on both A and B.