IP SLA Route Tracking

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Sep 8th, 2009
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Hi All,


I have setup IP SLA Route Tracking to monitor the reachability of a host via 2 links, so when 1 link fails, the route is removed and traffic is routed via the other link.


I wanted to know if there was a way to actually stop the failback from occuring (eg if link 1 is my primary link and it fails, then link 2 will stay my primary until it fails, then it will fail over to link 1 etc).


Our IGP is OSPF. I am redistributing a static route into OSPF with a higher cost from link 2, although I may need to change that to get the above solution working.


Thanks,

goulin

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Giuseppe Larosa Wed, 09/09/2009 - 00:15
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Hello Goulin,

so you are using reliable static routing with object tracking:

you have a primary path and a secondary path.

The local router is able to switchover to secondary path when primary path IP SLA test fails but when the IP SLA test provides again positive results you don't see the router to switch back to older primary path until the secondary fails?


In addition to this you are redistributing the static route(s) into OSPF.

IF the static route has a next-hop = link2 you see an higher seed metric.


I would suggest to post a filtered version of your configuration about the static routes the IP SLAs and OSPF.


A useful debug command can be

debug ip routing


that accepts an ACL as a parameter so you can define a filter use an ACL that specifies the IP network of the two static routes.


Hope to help

Giuseppe


goulin Wed, 09/09/2009 - 02:43
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Hi Giuseppe,


Thanks for your response. Just to clarify. I have 2 routers performing IP SLA, that are both injecting the same routes into OSPF. My primary router inserts the route into OSPF with a cost of 1. My secondary router inserts the route into OSPF with a much higher cost.


When the primary path fails, the primary router removes the route, and the route via the secondary router is preferred.


What I am trying to achieve is when the route fails over from the primary to secondary router, I want the secondary to remain the primary path, even if the route via the primary router comes back up.


Then... if the primary route (i.e. the route from the secondary router fails), I want it to fail over to the primary router.


I hope that makes sense.


Thanks,

goulin

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