I recently witnessed a very strange problem with BGP route reflection, and would really appreciate some pointers.
Although I have worked with BGP quite a bit, my experience with Route Reflectors is fairly limited.
Please refer to the attached diagram for the network topology...
Based on the RR theory that I read, referring to the diagram, any eBGP-learned routes that Router3 learned should be reflected by RR01 to Router4, and vice versa. HOWEVER, I noticed that this route reflection did NOT take place, which caused a big issue when we performed fail-over testing. When we shutdown Router3's interface connected to Router5, RR01 did not reflect the redistributed EIGRP 102 routes learned from Router4 back to Router3, hence Router3 has no knowledge of EIGRP 102 network anymore. Since Router3 is still considered the Master HSRP, packets sent by the Firewall towards EIGRP 102 network gets black-holed by Router3.
Unfortunately, I'm bound by confidentiality agreement preventing me from publishing any parts of the configs here. And, considering the size and complexity of the configs, it would take too long to modify them.
Is there anything in particular that you're after?
1. Good question. I don't remember exactly, to be honest. Despite our advice, the customer decided to connect dozens of production servers to the network, although we have not performed any testing on the new network. When we did the testing, we had to do it in a hurry, and forgotten to capture any IOS outputs. As far as I remember, eBGP routes learned by Router1/Router2 and/or directly by RR01/RR02 were reflected properly to Router3.
2. Yes, RR01 is definitely reflecting/advertising all the routes it learned to Router3. I could definitely see all the routes from "sh ip bgp nei advertised-routes" command on RR01. Funnily enough, when I did "sh ip bgp nei received-routes" or "sh ip bgp nei routes" from Router3, I could not see any EIGRP 102 routes that RR01 learned from Router4.
BTW, I forgot to mention that there's absolutely no filtering within the RR cluster. One other indication of the problem was when I inspected the BGP table on Router3, the EIGRP 102 routes only had 1 path while all other eBGP-learned routes had 2 paths.
The following are the IOS versions and platforms that we run, by the way. Should've included this info initially...
- Router1/Router2: Cisco 3825 ISR, 12.4(4)T4 Advanced IP Services
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