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MPLS and OSPF with backdoor links. Sham-links not an option

Unanswered Question
Feb 9th, 2012
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I in the middle of a conversion to an MPLS network from a s layer two network and have ran in to an issue with my redundant links.

Our network is a 20+ site network. The primary network is in a hub-spoke configuration with our telecom provider as the hub and with some fat spokes as needed. For the backup network we are using a DMVPN over 3g.


We were running EIGRP but the telecom wasn't able to support it over there mpls so we converted the network to OSPF to prepare for the migration.

When we started turning up sites I notice that the MPLS network is advertise is E2 links were as the DMVPN is advertised as inter area. So since inter area is preferred by OSPF the router started routing traffic over the backup links. To resolve this I temporarily shut off the backup links on the converted sites.



I talked with our telecom provider asked if they could setup sham-links. They got backed to me a few days later and said after a review with their engineering group they will not support sham-links.



OK so the question, what is the best way to resolve this issue without sham-links?


Option 1.

Setup a second OSPF process for the redundant links then redistribute that route into the main OSPF process as E2 links


Option 2.

Setup EIGRP with a higher administrative distance for the redundant links


Option 3??????? Is there some other option ??????



I'm wondering what would be best, has anyone set this up in a production enviroment with success and reliability?

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ebarticel Thu, 02/09/2012 - 15:04
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3. floating static route with AD higher than OSPF and redistribute into OSPF.


Eugen

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