Thought I would share
3.3 - Config EBGP sessions between R2 and AS22 as well as R2 and R4 and R5. All routers should see AS2 and AS22 as a single AS222 I was thinking confederations but I was thinking of an easier (lazy) way and decided to go with "local-as 222 no-prepend replace-as" , R4 and R5 believe they are peering with AS222. Then I configured the peering with AS22 (BB router) from AS2 (R2) and t bang (I was not sure how BB is configured - I try never to look at the BB routers) Sep 17 00:18:48.470: %BGP-6-ASPATH: Invalid AS path (22) received from 135.211.222.22: Non confederation peer Shortcut rejected.........back to confederations It was a great learning experience I also now know that a confederation mismatch will spit out some meaningful info DSG shows the answer leveraging confederations
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