Cisco – How to announce IP address in BGP on Cisco router

I see that this question was asked in April 2010. Good news is that four years later (April 2014) Cisco released ASA software version 9.2(x) with new BGP support! See the ASA 9.2(x) release notes for details. If you're using the ASA 5505, you should review the 5505 RAM requirements listed in the release notes.

ASA users have been asking for this feature for a long time - it's good to finally see it delivered :-).

Well, you're way over complicating the issue. You don't need to even think about route reflecting with just 4 routers. Just have them all peer with one another. However:

The important thing to keep in mind is that routers B and C don't "know" that they are route reflector clients. Router E knows that, though. So in this case you would just peer router D with router E (normal IBGP like you have with 192.168.3.1) and that's it.

When a router is configured with the attribute 'route reflector client' towards an IBGP peer, what that means is "I will pass on all of this routers routes to all my other IBGP neighbors", whereas normally, each router would only send its own routes to other IBGP neighbors.

i.e., towards router A (EBGP neighbor router D), D will just do its normal policy towards an EBGP neighbor - it will send every IBGP route that it has, not just its own. It doesn't matter if they were reflected via E from B or C - it's not important how they arrived at D.