Pls, refer to the document to answer the question.
R1 is in different AS, R2 is in different AS.
My router R has connections to both AS.
Imagine: (Determine route from R to AS)
1. Next hop is reachable
2. Local preference is the default value which is 100
3. AS path is also the same.
4. All routes have originated from iBGP, hence origin is also the same.
5. By default, MED can't be compared between two different AS. We can go for load balancing. However, I have placed 'always compare MED' in the configuration. Both MED is compared and unfortunately, it is the same.
6. Prefer the External path. Both paths are external.
7. Prefer the metric. Unfortunately, both are same which is 10
8. Prefer the route with lowest router ID. Both are same.
9. Prefer the lowest cluster ID. Here, also both are same.
10. Prefer the lowest peer ID. It is also the same.
My question is what happens when all the route attributes fail. What will happen next? How does the route propagate from R to any of the AS after 10th step?
Very eager to know about it.
there are three more selection criteria (see document attached). The last criteria is to prefer the path that comes from the lowest neighbor address (that is, the IP address configured with the 'neighbor' command).
in theory, one of the criteria should apply. If you have a test lab, you might want to test and see what happens when all 13 criteria are identical. I have never seen it, and the guys writing the BGP RFCs thought it through (I suppose), so in real life, there should never be a situation where all 13 are the same...