BGP Show n Tell #1: eBGP Peer (IPv4 and IPv6) R2 and R20
eBGP neighbor up R2 and R20 with IPv4 and IPv6
This blog is a weaving together of 5 YouTube videos. With links to the topology pdf as well as 2 pcaps.
SPOILERS:
We will see that both IPv4 eBGP and IPv6 eBGP peering will not come up between R2 and R20 because R20 is has the wrong AS number configured for R2.
– Configure R2 to eBGP peer with R20 via IPv4 address
– See that the eBGP peer isn’t coming up
– Notice that the physical interface on R2 going to R20 is admin down
– No shut the interface
– See that the eBGP peer is still not coming up
– Notice in the logs on R2 that there is a BGP notification being received from R20 that R20 views that the peer is in the wrong AS
– Go to R20 and see that the neighbor statement to R2 is configured to be AS 100
– Fix this and change it to AS 10
– Go back to R2 and see that the eBGP peer is up and we are receiving prefixes
– Configure R2 to eBGP peer with R20 via IPv6 address
– See that the eBGP IPv6 peer isn’t coming up
– Notice in the logs on R2 that there is a BGP notification being received from R20 that R20 views that the peer is in the wrong AS
– Go to R20 and see that the neighbor statement to R2 for eBGP IPv4 peering is configured to be AS 100
– Fix this and change it to AS 10
– Go back to R2 and see that the eBGP IPv6 peer is up and we are receiving prefixes
ipv4
