VPN between 1841 routers - how to route traffic

[beatdown]

Our headquarters has an 1841 router, and a Watchguard firewall. The router has a very basic config, and NAT is done at the firewall. We have some branch offices with similar setups, and intra-office communications takes place via IP-SEC VPN tunnels between the Watchguard firewalls.

We have a new branch office that just has an 1841 router. There is no firewall, so NAT is done on the router. We want to setup a VPN tunnel to the branch office, but it won't work from our Watchguard firewall, to the branch 1841.

So I'm thinking we can set up the VPN between our headquarters 1841 and the branch offices 1841. My question is, how would I set things up to route traffic between the headquarters 10.10.1.0/24 network, and the branch offices 10.10.5.0/24 network. From what I understand, normally routing between private IP networks is done on the device thats doing NAT and VPN, which is the Watchguard firewall at HQ. So how would I make this work in my situation?

Can anyone clue me in, as to how to make this work?

Thanks!

 

[makemorebeer]

i'm not sure how the watchdog comes into this but i've got a site to site VPN running with GRE Tunnel. this creates it's own subnet that runs tandem to your network. then you route to the tunnel interface and magically it comes out the other end. i've been using mine for about six months and it's been working like a charm. the route the ACL's (in your case watch dog) just needs to allow GRE, and i think isakmp traffic. not sure off the top of my head what ports these are.

 

[daffymd]

You would need to create a VPN from the Branch Office 1841 to the HQ Watchguard.
Not done it myself but there are some examples of Watchguard to Cisco PIX here to at least get you heading in the right direction.

http://www.watchguard.com/support/interop/interopVPN/interopvpn.asp