I have a question and one can refer to the diagram and explanation given at the following link as reference.
I need some fine tuning of my understanding of BGP synchronization and advertisements.
With the synch rule, an eBGP speaker must wait for its IGP to converge before advertising a prefix to an eBGP neighbor (different AS).
That makes sense and its easy to understand why. What I have been wondering is how the eBGP speaker knows when an IGP neighbor has converged. In the diagram, how does router B know that router E has learned of network 220.127.116.11?
Yes, router B can see the route for 18.104.22.168 in its own IGP table, but does that necessarily mean that router E's IGP has been informed? Let's say that router B's IGP was informed through another router, router Z. So, that tells router B that router Z's IGP process knows of 22.214.171.124, but what about router E? The importance of router E's IGP process knowing of the route, of course, is as explained in the dialogue -- router B knows that 126.96.36.199 is hanging off of iBGP neighbor router A, and he knows that to forward traffic to 188.8.131.52, he must go through router A. To do that, he has to go through E. So, bottom line, how does router B know whether router E's IGP process is informed of the route?
Am I confusing anyone?
I would love to hear from the senior engineers on here, especially.
Thanks very much