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List:       cisco-nsp
Subject:    [c-nsp] OSPF + metric / cost
From:       CiscoNSP List <CiscoNSP_list () hotmail ! com>
Date:       2016-02-13 22:39:49
Message-ID: CY1PR13MB008006A0213323AF4ED5F3F28AAA0 () CY1PR13MB0080 ! namprd13 ! prod ! outlook ! com
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Hi Everyone - Have the following scenario:

POPA - 2 ASR1ks acting as RR's

ASR1 has a 1Gb link to POPC via POPB - POPC has IPTransit gw
ASR2 has a 1Gb link to POPD - POPD also has IPTransit gw, and a 1Gb link to POPC
ASR1+ASR2 are also directly connected

I have both IPtransit routers sending defaults to both RRs - Preference for the RRs \
default is POPC (Set via weight) as this gw is 2m/sec away, compared to 20m/sec to \
POPD.

Link from ASR2 -> POPD was unused, unless link(s) to POPB/C failed - I wanted to use \
this link for prefixes that were "local" to POPD....achieved this by setting a lower \
OSPF cost on this link....everything "appeared" to be working as I wanted (Prefixes \
local to POPD were now using the previously dormant link) - but this created a \
problem with ASR2's "preffered" path to POPC...It saw the link to POPD->POPC as the \
shortest path....this obviously wasnt what I wanted, as it increased latency to the \
Internet for any tail connected/using ASR2 (ASR1 still saw the link POPB->POPC as the \
"best" path)

So, Im wondering if it is possible (via OSPF?) to have ASR2 see the path to POPC as \
"best" via POPB, but also still utilise its direct link to POPD for local \
prefixes...Ive played a bit with OSPF cost, but as soon as I lower the cost from \
ASR2->POPD enough for it to be used for local POPD prefixes, ASR2 starts using this \
link to get to POPC.

Note  - OSPF is only used for loops+p-t-p link IPs, iBGP is used for all "other" \
prefixes

Cheers for any  suggestions.

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