I have 3 sites, 1 head office, and 2 branch offices. Head office can ping the routers & server in each branch office, and the branch offices can ping the router and server in head office, but the branch offices can't ping each others servers or routers. Each site has a domain controller, and runs a distributed file system for user data.
Head office is on IP address 192.168.5.0/24. We have 2 routers here, both Draytek 2820's. 192.168.5.1, this is for general internet access * incoming emails. Then we have the site-2-site VPN router which is 192.168.5.2 (we need 2 ADSL lines as the speed is only 500kb upload, 1mb download). The server is 192.168.5.20.
Branch office1 is 192.168.4.0/24, there is only the VPN router (Draytek 2820) which is 192.168.4.1 server is 192.168.4.20.
Branch office2 is on 192.168.0.1/24, only the VPN router (Draytek 2820) which is 192.168.0.1 server is 192.168.0.20
The default gateway at head office is the internet router, 192.168.5.1, so I have added a static route to the server, uisng 'route -p add 192.168.4.0 mask 255.255.255.0 192.168.5.2 metric 1' and the same for the 192.168.0.0 network, so it knows how to get to the other networks. The other networks both had a route added for head office, which worked, and for each other, but this didn't work!
How can I get branch office1 and branch office2 to communicate? Do I just need to create a site-2-site VPN between each of them? Would this cause a network data loop, and bring the whole network down?