At 01:16 PM 01/08/2001 +0530, Vinod Anthony Joseph Cherunni wrote:
>Vinod,
Comments inline,
>Dear All,
>
>Here I am once again with a query in mind. Taking a scenario having two routers interconnected with each other over a Point-Point link, wherein each router has a dual connection to the Internet to different upstream ISP's. Now if I have configured two default routes in each direction as follows -
>
>Router A
>route 1 = ip route 0.0.0.0 0.0.0.0 ISPA admin-distance = default ie 1 (Primary link)
>route 2 =ip route 0.0.0.0 0.0.0.0 ISP B admin-distance = 150 (Secondary link)
>
>Router B
>
>route 1 = ip route 0.0.0.0 0.0.0.0 ISPA admin-distance = default ie 1 (Primary link)
>route 2 = ip route 0.0.0.0 0.0.0.0 ISP B admin-distance = 150 (Secondary link)
>
>Also Now I have configured both my routers to propogate a 0.0.0.0.0 route using the "default-orginate" command into the OSPF (Single Area) domain as External Type 1 route which has an administrative distance of 110 by default.
>
>The requirement is such that if the primary link in router B (route configured with default administrative distance) fails, Then router B should propogate the OSPF default-originate route with a high cost, so that router A will not choose that route While router A's primary link is also down, & ahould choose the locally available seconday route
cost (metric) comparison only happens between two routes when the Admin Distance are equal. In your case 0.0.0.0 advertise by B, will have an Admin Distance of 110 (ospf AD) in A and therefore will select this over secondary static default in A (AD = 150). Cost will play no role in this.
>The idea is as follows -
>
>1. Both routers should choose the static route to the primary link locally if available.
this should happen.
>2. If the primary link fails in one of the routers, then the router which is affected should use the remote router's locally available primary link.
This will also happen but you are contradicting your statement few line above.
>3. If both the primary links fail on both the routers, Then each of the router should only use its locally available secondary link.
This will not happen as explained above. Secondary static 0.0.0.0 will not be used because OSPF 0.0.0.0 will win.
>4. If any one router even losses its locally available secondary route, Only then it should use the seconday link available on the remote router.
>
>The reason being all the secondary links are planned to be used for catering to MPLS customers, & we plan to save on that bandwidth. This is a stopgap arrangement.
>
>A small thought, can both the routers be configured with route-maps that would effect the administrative distances of the propagated OSPF default routes in certain situations.
I think you need to clarify your requirements as they are contradicting. In any case your requirements are easy to manage, so just clarify us and we should comment.
Thanks
Zaheer
>Kindly advice,
>
>With warm regards,
>Vinod.
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