I'm setting up a second site for redundancy and DR.
The goals are as follows:
- ISP fault-tolerance from either site: HostA, for example, can reach the internet in the event that ISP-A(primary) and ISP-B go down.
- Similarly, servers will continue to be accessible from the internet in the event that 1 or 2 connections are lost.
- We already have Router-A connected via BGP among two ISPs. Either ISP can go down and we can continue to function, so assume that the initial BGP/ARIN steps are completed.
- EDIT: sites interconnected via 1 or more 1gbps private lines
- EDIT: Routers are also firewalls in this case
- How do I handle the default gateway situation?
- Do I point clients in their respective sites at their respective router? What if that router loses connectivity?
- What about asynchronous routing? Say ISP-A is our primary and traffic comes in destined for a server on Site B (who is pointed at Router-B for default GW), won't that cause issues? Ideally we wouldn't have such a situation even if it means designating one router as default GW for all and have it route to the second router in the event it loses it's ISP connectivity.
- I was thinking I needed something like OSPF to propagate the awareness of ISP link failures, but I'm not clear on what it would help.