I am testing a redundant internet connection setup that works like this -
I have a network segment, 192.168.80.X It has two gateways - 192.168.80.1 - a FW connected to a frame relay line 192.168.80.2 - an ADSL modem/router
I set up a windows server with a static ip 192.168.80.10, subnet 255.255.255.0 and two default gateways - 192.168.80.1, 192.168.80.2 and set the metrics manually to give the frame relay line preference.
Both routers have port forwarding set up to forward port 80 from the WAN address to the server.
The problem is that when the default gateway selected by windows is 192.168.80.1, it won't accept incoming connections coming from the ADSL router, and vice-versa - if the gateway selected is 80.2 then connections coming to the WAN address of the FW don't get through.
Is this kind of setup even theoretically possible? If it is, I assume it's a routing issue that needs solving? Perhaps adding a route manually to the server/WAN routers?
I'm not networking-savvy enough to figure it out on my own.. some help will be appreciated.
Thanks!
It isn't that the incoming connection isn't coming it, it's that the routing table thinks that the return trip should go through the default gateway.
You should really consider splitting this off into 2 different subnets for the LANs between each WAN device and the server's NICs. That would be the proper way to handle this, and if it is a direct connection between the server NIC and a port on the "gateway" then something as simple as a /30 would work for each "route".
Use 2 different NICs in the Windows Server, each on their respective subnets and respective default gateways to each of these WAN devices. But you'd still have to manually fail over the gateway in the routing (disable one nic for instance during normal operation, and then enable it and disable the other during failover. It would all be manual).
I don't know if RRAS and dead gateway detection might work here...never used it myself, but you may look into it too.