On Fri, 12 Jul 1996, Paul Ferguson wrote:
I'm sorry, but I'm afraid that you're missing the point here.
In most larger ISP backbones, the behavior of their IGP is indeed visible to the public, since in most instances, most of the Internet traffic relies on the stability of these interior (an esoteric term) networks. Therefore, whether interior or exterior flap is really of no relevance in this context.
<This isn't intended to irritate, I just want to make sure I understand this correctly> Let me try a very simple example: To Internet To Internet <-- Peering points or upstreams 'Point A' 'Point B' | | +-----------+ +-----------+ | Router A |---| Router B | +-----------+ +-----------+ | | | | +-----------+ +-----------+ | Router C | | Router D | +-----------+ +-----------+ | | To Downstream To Downstream Non-BGP (Static) Non-BGP (Static) Customer Customer Routers A & B are running BGP to the outside world, and iBGP between them. Routers C & D are 'defaulted' into A and B. If the link between A&B dies the Exterior Routes will (and should) flap. If the link between either A or B and the Internet dies, the Exterior Routes will (and should) flap. If the line between routers A&C or B&D or between either C or D and their respective static downstreams die, there should be NO external route flap. However, if C&D are incapable of 'Null0' routing, it may be beneficial to run dynamic routing between A&C and between B&D so that A&B discard packets instead of causing a routing loop. This "internal routing flap" should not be visible to the outside world. I think that's what I meant to say before. Sometimes I'm not too clear about what I'm saying. If I've still missed the boat feel free to let me know :) -forrestc@imach.com