How do I configure BGP conditional advertising such that it stops advertising if it loses certain networks?
I want BGP to track certain networks learned via an IGP, and if it loses these networks due to an outage or link failure, I want it to stop advertising these networks to its peers.
Given: Networks A, B, and C are learned via an IGP.
Goal: I want BGP to summarize A, B, and C as D, and advertise D to its peers.
Restriction: BGP is to only advertise D if A, B, and C are all present in the routing table. If any one of A, B, or C is missing, BGP should not advertise D. For example, if C is not present, but A and B are, BGP should not advertise D.
I will use the aggregate address command to create D.
However, I am unsure how to create the condition that makes BGP ensure that A, B, and C are present before it advertises D. I am currently researching the advertise map, but I don't know if that will do it.
Does anyone have any pointers or suggestions, or can confirm I am heading in the right direction?
If you use the aggregate command, do you need individual network statements for the networks summarized?