3) Router Configs Explanation

On R0:
You might have noticed the distribute-list commands under the BGP neighbor configuration, I did that to prevent the networks from the AS 30 and 50 from getting to AS 100 and vice-versa. And this is actually the danger in multi-homing in a single router into 2 different ISPs; you have to prevent each others network from crossing you. I actually tried different methods but I ended up doing the easy but not flexible way and in real world you don't want to do it in this way.

As I create this blog I actually thought of a better way and you might want to try it in this LAB. Maybe we can create a deny route-map with two match clauses then apply the route-map out into the neighbor bgp configuration. The two match clauses should be a standard permit any ACL and as-path access-list with a regular expression of "^[AS Number]_". The Reg expression "^[AS Number]_" means received from a router with the AS Number specified, so the combination of ACL and as-path list interprets to any ip/network that we received from the router that has the AS Number we specified. If you decided to try it out please send me a feedback regarding the results, I may not be able to try it myself but once I have the time I'll definitely try it out.

Alright, I actually tried this one, please see the "Tips and Tricks" post.

And on the 2 ACLs named "AS-PATH-100" and "AS-PATH-30-50" I denied the 192.168.0.0 network in that way we can really be sure to prevent R0 from re-advertising that network to the other ISPs. (But we wont need to do this anymore if we implement my suggestion above.)

On R5:
This router should have the same case as with R0, you already know the issue and you have read my suggestion about what we can do, and now its all up to you to try it out.

On R1-R4 and R6-R7:
These routers are all configured in the same fashion/manner. All routers in their respective AS'es are in full mesh IBGP configuration and they are peering to each other through their Loopback IPs and only the Loopback IP address are the ones getting redistributed into BGP. The OSPF job is to create a Layer 3 connectivity in between the Loopbacks to help IBGP routers to form neighbor relationship with their peer router.