While waiting for my allocation to be actioned and having little or no experience I decided to experiment to learn more about the use of the tunnel interface and what would be possible with it.
I have all ports forwarded from my ISP's modem to a PC I am using as a router. I have a tunnel set up on a one to one basis with a forwarding partner and it works well.
My router PC has three network cards, one with a 192.x.x.x/24 address and the other two with a 44.x.x.x/29 and 44.x.x.x/27 address.
Connections between both 44.x.x.x addresses work with my forwarding partner and I can forward between my 44.x.x.x addresses using [ eth0 ] but not when I set the route at each via [ tunl0 ].
Is it something simple I have missed ??
Assuming - your PC has an IP from all 3 networks - you have correctly configured the net mask for each interface
then your operating system automatically creates the necessary routes in your routing table. These are called "connected routes", because your PC has an IP address within that network, it is directly connected and it don't need manually added routes aka "static routes" to find other hosts within those networks.
You only have to add static routes for networks that the PC doesn't connect to directly.
So routing your local networks, which are usually physically accessible via eth0 and/or eth1 and so on, via tunl0 will obviously create issues, as your local networks are on the physical interfaces eth0, eth1, ethN ... but not tunl0. Remote 44networks, e.g. networks you are not directly connected to, are reachable via tunl0 (assuming the necessary configuration)
73 de Marc, LX1DUC