Remote LAN Redundancy

dhardy6786 · ‎08-17-2008

We are in the process of building a disaster recovery center several miles away from our main campus, which has been made accessible via a high bandwidth Ethernet connection over radio. Rather than creating a new subnet for this location, it has just become an extension of the main campus. We decided to try this for redundancy purposes.

The disaster center has a bundle of T1s of a lesser capacity than that of the main campus. Of course, when the radio fails there is only one way to access the disaster center. Obviously, because it is the exact same subnet, the main campus wins out the best path to the subnet in the OSPF area. This naturally creates a situation where users on campus can't make it out of the local subnet destined for addresses at the disaster center, and users external to the campus subnet don't have the proper route for those same addresses.

I just have a few questions about this situation. Is this even the way we should be doing it? Are there any other design recommendations for purposes of the network infrastructure that we have available to us? Is there a solution to the obvious routing problem we have here?

Thanks for any input,

Daniel

mohsin.khan · ‎08-18-2008

We are doing the same in our network,i.e. using the same subnet for different sites, but it would be great if you could share a diagram of explaining how r u connecting users to those sites, and what mechanism are u using for DR?

dhardy6786 · ‎09-18-2008

I've attached an example of what we are doing. I've come to the conclusion that by NATing the Disaster site, when it becomes primary it should resolve the issue of routing, but then I don't know if this best practice. Nor do I know if combing both sites like this is best practice. Same for redundant NICs, one in each subnet. It just seemed convenient at the time of design. The site was never meant to be used while both sites are active, however a recent problem forced us to activate such a plan. In the event we had this happen again, and the radio was actually down, you see the issue here.