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This sounds an awful lot like a problem we saw awhile back when upgrading from JUNOS 4.x to 5.x. At some point (I don't remember exactly when, but the details should be in the case notes of PR.19592) Juniper implemented a change that which makes their box compliant with RFC 2858. However, when speaking BGP with a non-RFC-compliant box (such as a Cisco running something like 12.0(15)S) the session flaps continuously in the manner you describe because the other box expects the NEXT_HOP attribute to be present in every update message. attribute in an UPDATE message if only the MP_REACH_NLRI attribute is present. A workaround is to only use family inet unicast instead of multicast or any on all BGP sessions to those cisco routers or upgrade all of the cisco routers." <snip>
Anyone have a Cisco BugID for this?