Hi Aijun, > How to revoke the UPA explicitly when the prefix is reachable again?
In link state protocols when LSP/LSA is readvertised without UPA that is equivalent to withdrawing it - but I think Peter already indicated that at least twice here. > Please note “stopping sending UPA” is not equal to “revoking the UPA”. > For example, in BGP, when you want to revoke some prefixes, you will > advertise explicitly “withdrawn” prefixes , not just stopping sending the > related BGP Updates. Yes it is very different in distance vector protocols ... I don't think LSR can't help with that :( Thx, R. On Fri, May 30, 2025 at 1:09 AM Aijun Wang <[email protected]> wrote: > Hi, Robert: > > We are discussing how and when to back to the normal state before UPA is > triggered, not how to configure BGP active/backup via Local_Pref Attribute. > > Or, let’s change the statement in more general manner: > > How to revoke the UPA explicitly when the prefix is reachable again? > > Please note “stopping sending UPA” is not equal to “revoking the UPA”. > > For example, in BGP, when you want to revoke some prefixes, you will > advertise explicitly “withdrawn” prefixes , not just stopping sending the > related BGP Updates. > > Aijun Wang > China Telecom > > On May 29, 2025, at 18:33, Robert Raszuk <[email protected]> wrote: > > > >> >> Once that’s done, the ABR can safely withdraw the UPA, and the network >> remains stable (i.e. from R1 perspective the backup egress router became >> the new primary egress router once BGP converged because session with R2 >> failed). >> [WAJ] Then, R1 will keep using the backup egress router forever? When, >> how and what trigger the R1 switchback to the original egress router? >> >> > Even without UPA at all in the picture if operators chooses active/backup > scheme (as opposed to active/active model) for multihomed sites or networks > typically BGP paths carry properly set LOCAL_PREF attribute. > > UPA does not have anything to do with it. > > Thx, > R. > > > > >
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