You're the best Oli Thank you very much for clarifying the multipath-protect feature. Right for multipath there are alternate paths installed in FIB already so in case one fails others serve as backup.
I've just realized I forgot the "advertise best-external" cmd in configs below -which is necessary to get the alternate paths propagated across the network Now to my question I was strongly advised by the SE team NOT to use the combo of multipath + backup-path: The reasoning behind it was basically that it was not tested by big ISPs -so I guess no one really knows how it behaves in production networks. I also heard an argument that best-external could cause loops in some cases -though I can't really think of such a scenario -and would love to be schooled on that. router bgp 123 vrf test address-family ipv4 unicast additional-paths selection route-policy RP-PIC advertise best-external maximum-paths eibgp 8 So please are there any issues/corner cases where it can cause issues -or it's just a lack of production testing? adam -----Original Message----- From: Oliver Boehmer (oboehmer) [mailto:[email protected]] Sent: Tuesday, January 08, 2013 5:55 PM To: Adam Vitkovsky; [email protected] Subject: Re: [c-nsp] IOS XR PIC (+ multipath) Adam, > >More specifically with the new CLI for the feature in 4.2 : > >route-policy RP-PIC > set path-selection backup 1 install >end-policy >! >router bgp 123 > address-family vpnv4 unicast > additional-paths selection route-policy RP-PIC > > >I'm more interested in the advanced multipath/primary-backup >implementation: > >-so for equal cost paths I'll have the balancing in place -and for >unequal cost paths I'll have the PIC in place well, no. For equal-cost, you also have PIC in place, but as the router already has two (or more) path installed and active in the FIB, it doesn't need to install a backup path. so that's PIC-like behaviour, without any config. The config ... > >route-policy RP-PIC > set path-selection backup 1 install multipath-protect end-policy ... also causes the PE to install a backup path even for those cases. I can't think of a scenario where this is needed, but I might be missing something. oli _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
