The company where I work is in process to become an Autonomous System. We'll request an AS number and an IP block to the RIR.
I've attached a picture which shows what we are thinking to do.
Today we already have these two ASA running as active/failover connected to only one ISP through a Cisco router which has only a default route.
Basically I'm adding a second router connected to a second ISP.
Here are our requirements:
- We don't want full internet routes.
- We should load balance Upstream and Downstream traffic however failover is the most important.
That's our thoughts:
1) Obviously we need BGP.
2) Suppose we have a /22 block, we want to propagate /23 in each ISP and if Router or Link to that ISP fails it should propagate /22 to another ISP. Is that possible? Could you point me any paper to read or some example about that?
3) There's an option to propagate /22 in one ISP and the second ISP is just a backup. Is this better than previous option?
4) Since ASA5500 doesn't has BGP, we think to run OSPF/EIGRP between border routers and ASA and distribute default route to ASA. And this is the most confusing to me: If we are dividing /22 into two /23 how it will decide where to send traffic. In fact I'm still not "seeing" how this scenario could work. I would like to hear your opinion if this is the best to do and if not, what is recommended.
I appreciate any thoughts