[j-nsp] iBGP routes and prepends - Cisco vs Juniper behaviour

[Pedro Roque Marques]

lerik at nolink.net (Lars Erik Gullerud) writes:

> However, the Juniper boxes ignored the routes completely

It discards them when they are received since they are looped...

> 
> A quick perusal of the BGP RFC didn't seem to shed any light on which
> behaviour is "correct"

>From draft-ietf-idr-bgp4-18.txt:

9. UPDATE Message Handling

   An UPDATE message may be received only in the Established state.
   When an UPDATE message is received, each field is checked for valid-
   ity as specified in Section 6.3.

   [...]

   The information carried by the AS_PATH attribute is checked for AS
   loops. AS loop detection is done by scanning the full AS path (as
   specified in the AS_PATH attribute), and checking that the autonomous
   system number of the local system does not appear in the AS path.  If
   the autonomous system number appears in the AS path the route may be
   stored in the Adj-RIB-In, but unless the router is configured to
   accept routes with its own autonomous system in the AS path, the
   route shall not be passed to the BGP Decision Process. Operations of
   a router that is configured to accept routes with its own autonomous
   system number in the AS path are outside the scope of this document.

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My understanding is that this check is applicable to both e and iBGP
updates.

  Pedro.