Next hops are part of the IGP summary when advertising outside of the area. Within area those are host routes usually or smaller subnets (/24s for TOR-Compute LANs).
Thx, R. On Thu, Nov 18, 2021 at 3:17 PM Aijun Wang <[email protected]> wrote: > Hi, Robert: > > If you use iBGP in your mentioned scenario, how to propagate the > reachability of BGP nexthop? I think it is impossible to use again BGP > itself. Then depend only BGP can’t solve your problem. > > If the underlying using IGP to propagate such reachability information, we > have mechanism to control for which covered prefix to send the notification > when they become unreachable. It is not randomly suppressed. > > > Aijun Wang > China Telecom > > On Nov 18, 2021, at 21:27, Robert Raszuk <[email protected]> wrote: > > > > In such cases I would rather consider implementing pulse to be less then > host route. > > Suppressing them randomly may lead to even bigger disappointment of > unreachability propagation hence delaying connectivity restoration to a > backup path. > > Many thx, > R. > > On Thu, Nov 18, 2021 at 1:58 PM Peter Psenak <[email protected]> wrote: > >> Robert, >> >> On 18/11/2021 13:42, Robert Raszuk wrote: >> > [WAJ] In the scenarios that you mentioned, BGP nexthop reachability >> > is derived from the directed interface, there is no summary action >> > done by the router. Is that true? >> > >> > >> > Not necessarily - TORs do not always do eBGP to compute and set next >> hop >> > self. There can be IBGP session there and therefor next hop is not >> > changed all the way to the remote compute. But the point was that today >> > BGP is involved already in reachability and service distribution. >> > >> > And while current IGP proposals can propagate this too the point is >> > about scalability when it comes to signalling of such massive failures >> > in the IGP. The amount of IGP traffic and processing in those moments >> > may be significant. >> >> we can certainly address such case by not allowing thousands of pulses >> to be generated in case half of the universe falls apart. That seems >> obvious and easy to implement. >> >> thanks, >> Peter >> >> > >> > And yes I agree this is not really a "hole punching" ... that was just >> a >> > description shortcut I used. >> > >> > Thx, >> > R. >> >>
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