OSPF Prefer MPLS over DMVPN

Answered Question
Jul 10th, 2009
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I have a MPLS network running BGP redistributing into OSPF as external type 2 routes. I am setting up a DMVPN over DSL as secondary. They come in as inter area routes so are always preferred. I even placed a higher cost on the interface connecting to the DMVPN Hub. I also tried changing the administrative distance for external routes to 105, which would be less than the inter area, but neither worked...

Anyone have any ideas how I can prefer the MPLS links over the inter area DMVPN links?

Correct Answer by Giuseppe Larosa about 7 years 9 months ago

Hello Andy,


OSPF uses its own hierarchy of route types to choice the best path:

O > O IA > O E1 > O E2.


If the routes come in as O IA routes, that is remote site DMVPN routers are ABR if your addressing plan permits it you should summarize at area border with

area x range 10.10.10.0 255.255.254.0.


If this is not possible you need to:

use O E1 type for primary MPLS redistribution into primary OSPF process

use a secondary OSPF process for the DMVPN cloud that you redistribute in primary OSPF process as O E2.

Because O E1 are preferred over O E2 you should be fine.

You may need some form of route tagging and route tags based filtering for safety.


Hope to help

Giuseppe

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Jerry Ye Fri, 07/10/2009 - 13:17
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Hi Andy,


How about using floating static route instead of forming OSPF neighbor for the DMVPN neighbor:


router ospf x

passive-interface tunnel x

ip route 0.0.0.0 0.0.0.0 tunnel x 190


HTH,

jerry

Correct Answer
Giuseppe Larosa Fri, 07/10/2009 - 20:48
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Hello Andy,


OSPF uses its own hierarchy of route types to choice the best path:

O > O IA > O E1 > O E2.


If the routes come in as O IA routes, that is remote site DMVPN routers are ABR if your addressing plan permits it you should summarize at area border with

area x range 10.10.10.0 255.255.254.0.


If this is not possible you need to:

use O E1 type for primary MPLS redistribution into primary OSPF process

use a secondary OSPF process for the DMVPN cloud that you redistribute in primary OSPF process as O E2.

Because O E1 are preferred over O E2 you should be fine.

You may need some form of route tagging and route tags based filtering for safety.


Hope to help

Giuseppe

trippi Sun, 07/12/2009 - 19:47
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Giuseppe,


Thanks for your help.

I changed my MPLS to redistribute as E1 instead of E2.

On the DMVPN spoke I added in the OSPF config to redistribute connected as E2.

Worked like a charm.

Giuseppe Larosa Mon, 07/13/2009 - 01:41
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Hello Andy,

OSPF can be complex sometimes, but provides this range of route types that are useful in this kind of scenario.


Best Regards

Giuseppe


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