VPN a routers subnet with the router knowing about it

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voipair

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Apr 17, 2013
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Not sure how to do this or if even possible, not sure what routers or firmware could accomplish. Here is my idea of the hardware pieces (incl vpn) and how they fit.

Locations
a = First location with adsl tv modem combo and network we want to join
b = second location that wants to be vpn'd to network at location a
Hardware
router1 (adsl tv modem router) = this is at the first location and we want the remote locations to appear local. no vpn support, also serves tv
router2 = This is at location a and serves two purposes. Act as switch on network at location a, provide a vpn connection to location b
router3 = at location b and connects to vpn on router 2 at location a , acts as switch on network at location a

Poor Network Map
ISP at location a -> router1 -> Lan port to Lan port on router2 (this might need cross over cable) -> wan port of router2 to lan port of router1 -> VPN over internet -> router3 at location b.

End goal is the addresses served up from router3 are handed out by router1.

Issues I can think of
1) Might need crossover cable from router1 lan port to router2 lan port
2) Need router 2 and 3 to act as a switch and connect via vpn
3) May have to play with settings ( think i will have to enable multicasting to get tv served by router1 working out of router3)
4) Don't know which router will host the vpn, would be easier if router 2 did
5)


Settings i think i know will help
a) I think i can "enable transparent bridging mode" on router1 so router2 will get an ip direct from isp at location a
from this page http://telusinternet.blogspot.ca/2012/10/using-your-own-router-in-tandem-with.html



So does anyone know if this is possible and what i should be looking at for hardware. My experience is medium, have flashed tomato and dd-wrt to one router so i could use wireshark to record some sip traffic. also have understanding of iptables in linux but by no means an expert. Willing to try anything if this could work.

Thanks for any suggestions, Let me know if this is the wrong place to post or if you can recommend another forum to post in.

thanks
David
 
Solution
eibgrad
If the only requirement is that the device at location B has an ip address on location A, then it sounds to me like you just need a simple VPN, and routed will do just fine. Because that’s what a routed VPN does. You exist on both the local and remote network w/ IPs appropriate to both. And since this isn’t a security driven need, but simply an issue of which ip is used, you can use the simpler (if less secure) PPTP VPN (OpenVPN is overkill).
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eibgrad

eibgrad

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Feb 16, 2010
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This is the one thing that caught my attention:

"End goal is the addresses served up from router3 are handed out by router1."

That’s a very “technical” goal that doesn’t really tell us the purpose of this architecture. The reason I ask is, let’s suppose the purpose was “to gain access to network A’s resources”, or “to hide my IP address so I could access resources across borders”, or “create a single logical network”. All those would require different solutions.

For example, if you *literally* wanted to have router 3’s network obtain ip addresses from router 1, then you’d be looking at a “bridged” VPN, such as OpenVPN and a tap (vs. tun) interface. Each network would share the same network addressing (e.g., 192.168.1.x), be able to send/receive network discovery messages, even use the same DHCP server (although that’s usually not desired and can be prevented). IOW, the goal is to have one logical network, so there are effectively no distinctions between being at one or the other location. That’s much different than a “routed” VPN where you maintain separate networks, but merely want remote access to the other network’s resources.
 
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voipair

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Apr 17, 2013
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Purpose of this architecture is to be able to plug in a Telus TV set top box at a different house than the subscription is at. So when i plug it in at house B it sees router1 at house a and gets its ip address and tv signal from router 1 . Tap and Tun are new terms to me (have not looked at networking in a while), bridged network sounds like what i want, not a routed. I imagine a router as the hardware because it can have the software in it to allow it to host or be client to a vpn, and can also have dhcp turned off (act like a switch)
The reason i have not tried it yet is router 2 needs the tricky set up - act like a switch and also do that over a vpn. Was hoping there was a guide somewhere for this weird set up that probably no one else has ever needed. Would be great if router 1 could host a vpn but would be silly for the Telco to have such functionality built in the hardware.


"bridged” VPN, such as OpenVPN and a tap (vs. tun) interface."
Thanks that sound like the terms i didn't know that will help me research further. So i would set up router 2 with TAP (operating at layer 2) and turn off dhcp and set it up to host a vpn. Now my issue is how do i tell it be act like a switch but also have an address for incoming vpn connections (probably not common for switches to host a vpn)?

 
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eibgrad

eibgrad

Splendid
Feb 16, 2010
3,373
2
21,465
If the only requirement is that the device at location B has an ip address on location A, then it sounds to me like you just need a simple VPN, and routed will do just fine. Because that’s what a routed VPN does. You exist on both the local and remote network w/ IPs appropriate to both. And since this isn’t a security driven need, but simply an issue of which ip is used, you can use the simpler (if less secure) PPTP VPN (OpenVPN is overkill).
 
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