[c-nsp] OSPF Loop-Free Alternate Fast Reroute and repair path

[CiscoNSP List]

Ah - I think Ive found the answer to my own question..this prefix doesnt have the flag NodeProt(I think), as this prefix would share the same next hop router as the primary path...indirectly, later in the path...all others wouldnt...




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From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of CiscoNSP List <CiscoNSP_list at hotmail.com>
Sent: Friday, 30 September 2016 7:57 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] OSPF Loop-Free Alternate Fast Reroute and repair path

Ok - A little digging, I found "sh ip ospf rib xxx" to show cost on primry/repair paths....Im hoping someone can explain why for this particular dest prefix, the ASR920 sees the 7200's link as "best"....all other destination prefixes have Gi0/0/1 as repair, but have Flags: RIB, Repair, IntfDj, BcastDj, CostWon, NodeProt, Downstr...but for some reason, for this prefix, the nodeprot, downstream arent "seen"?


sh ip ospf rib xxx.xxx.76.207

            OSPF Router with ID (xxx.xxx.76.192) (Process ID 100)


                Base Topology (MTID 0)

OSPF local RIB
Codes: * - Best, > - Installed in global RIB
LSA: type/LSID/originator

*>  xxx.xxx.76.207/32, Intra, cost 226, area 0
     SPF Instance 46, age 07:03:12
     Flags: RIB, HiPrio
      via yyy.yyy.230.174, TenGigabitEthernet0/0/26
       Flags: RIB
       LSA: 1/xxx.xxx.76.207/xxx.xxx.76.207
      repair path via yyy.yyy.230.170, GigabitEthernet0/0/0, cost 253
       Flags: RIB, Repair, IntfDj, BcastDj, NodeProt, Downstr
       LSA: 1/xxx.xxx.76.207/xxx.xxx.76.207
      repair path via yyy.yyy.230.168, GigabitEthernet0/0/1, cost 229
       Flags: Ignore, Repair, IntfDj, BcastDj
       LSA: 1/xxx.xxx.76.207/xxx.xxx.76.207


Thanks

________________________________
From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of CiscoNSP List <CiscoNSP_list at hotmail.com>
Sent: Friday, 30 September 2016 7:39 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] OSPF Loop-Free Alternate Fast Reroute and repair path

Hi Everyone - Have some ASR920's that have just been deployed, and have just setup ospf+mpls on the Interpop links - One of the ASR920's has a link to a legacy 7200, that will be retired soon, and Ive set ospf cost very high on that link, as I dont want it used, unless all other interpop links fail....Ive tested about 50 destination prefixes, all have the correct primary + repair path (Being 10G link from ASR920->other POP ASR920, repair path being 1Gb cross-link to second ASR920, then its 10Gb link->other POP ASR920)....except one prefix....it for some reason has the correct primary path, but repair path it has chosen is via the 7200....why it is choosing this link as repair doesnt make sense (Based on ospf cost).....Is there anyway to check a destinations cost on the repair path? (I can manually work it out, which I have done(And it is way higher than the cost of the "correct" repair path)....but Im hoping I can interrogate the ASR to find out what it sees as the cost.....because e
 ven the loop of the 7200's best+repair path on the ASR920 is going via the paths of all the other prefixes Ive checked.


Thanks in advance.
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