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

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List:       cisco-nsp
Subject:    Re: [c-nsp] OSPF Loop-Free Alternate Fast Reroute and repair path
From:       CiscoNSP List <CiscoNSP_list () hotmail ! com>
Date:       2016-09-30 10:55:41
Message-ID: BY1PR13MB0182E47A4FC7E0B6B898E5B38AC10 () BY1PR13MB0182 ! namprd13 ! prod ! outlook ! com
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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...

________________________________
From: cisco-nsp <cisco-nsp-bounces@puck.nether.net> on behalf of CiscoNSP List \
                <CiscoNSP_list@hotmail.com>
Sent: Friday, 30 September 2016 7:57 PM
To: cisco-nsp@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@puck.nether.net> on behalf of CiscoNSP List \
                <CiscoNSP_list@hotmail.com>
Sent: Friday, 30 September 2016 7:39 PM
To: cisco-nsp@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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