...

Just guessing - you're seeing these events between midnight and 5 am?

Hm, couldn't reist this one: "which time zone"?

Just hinting that even though it's that time interval in the US, local time is different in other places around the world, so if this is causing disturbance, others are probably being hit in their working hours.

Heh, the "perpetual global maintenance window syndrome", eh? A very useful concept...

Besides, I was under the impression that to activate a new outbound roting policy on a Cisco, you could just modify / replace it, but that you would still have to do

router#clear ip bgp xxx soft out

to activate it. This means that the policy for an existing peer can be modified without having to remove the peering and reenable it shortly thereafter (something which would cause needless route flapping).

Somewhat true. The new policy would not be applied to routes that were already in the table, but would be applied to any adds/withdrawals that occur once the policy changes are placed in the configuration. This fact has a synergistic effect when you're making changes that affect lots of sessions. So a policy change made a significant time before a clear or soft clear could in fact result in flaps. Also consider: there are a lot of routers using traditional ACL's in their policies (as opposed to things like prefix-lists which have more granular editing features) which would necessitate removing the ACL completely and rewriting it with updated lines. Due to the above, a potential for leaks exists unless the session is either shutdown or deleted while acl's are being modified. If the sequence of events in a configuration script is not well thought out, the result could be what Ratul has observed in his study.

Regards,

- Håvard