OSPF static

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Apr 14th, 2010
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Hi


We have connectivity between our three data center through the OSPF protocol


SITEA

SITEB

SITEC all running on Area 0


all connected routes from 3 sites are advetsied through OSPF and working fine now my requirement is from SITE A i have also connected to External device (through the routed interface which is not running on OSPF) to reach our Branch office subnet


Now i need to advetise the static route for example :


ip route 172.31.0.0 255.255.255.0 192.168.168.2


to other 2 sites so that from SITEB and SITEC so they have to sent all traffic to 172.31.0.0/24 to the SITEA and to external Device


whether this will work when i start advertising STATIC ROUTE ( we have rout-map filter to advertise STATIC Route )


can i also need to know is there any possiblility that i can filter this static route only to SITEB not to SITEC


thanks

Vinu

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Tharak Abraham Wed, 04/14/2010 - 04:13
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Vinoth,


"redistribute static subnets" should work fine in this case.

you can include the metric as well as the metric types optionally too.


If you want to be more specific, then you need to match the route with an ACL, match it in a route-map and redistribute too !

Giuseppe Larosa Wed, 04/14/2010 - 04:29
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Hello Vinoth,


>> connected to External device (through the routed interface which is not  running on OSPF)


you need to advertise in OSPF that IP subnet or the external route will not be injected in OSPF: an OSPF external route cannot have an IP next-hop that is another external route.

you can use network ... area + passive-interface for this


then using red static subnets route-map mystatic


you can advertise it using a route filter specified by the route-map


>> can i also need to know is there any possiblility that i can filter this  static route only to SITEB not to SITEC


This is not possible in OSPF, once an external route is injected it will go everywhere but not to stub areas, you should put site C in a stub area


or you should use a distribute-list in on each router of site C to deny that route but this does not remove the  route from OSPF database


Hope to help

Giuseppe

Tharak Abraham Wed, 04/14/2010 - 21:45
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Giuseppe,


Could you please throw some more insight on why ospf will not redistribute a static route without advertising the subnet connected from Site A to the external device in the above topology ?


redistribute static subnet at site A

and

a default route at the external device pointing to the next hop at site A should do the job (?)


Warm Regards,

Tharak

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