Sabri Berisha wrote on 01/08/2020 20:03:
but because Noction's decision to not enable NO_EXPORT by default
the primary problem is not this but that Noction reinjects prefixes into the local ibgp mesh with the as-path stripped and then prioritises these prefixes so that they're learned as the best path.
The as-path is the primary loop detection mechanism in eBGP. Removing this is like hot-wiring your electrical distribution board because you found out you could get more power if you bypass those stupid RCDs.
Once you strip off the as-path in the local view, it's like the AS7007 incident desperately begging to happen all over again.
As long as route optimiser vendors ship their products with such deeply harmful defaults, we're going to continue to see these problems ad nauseam.
Nick