At 03:24 PM 01/08/2001 +0530, you wrote:
>Thanks a lot for the advice, I think I have been unclear with the language I have used. Sorry for that.
How about not announcing the default when Primary is down and each router is configured with 3 defaults
1st default to primary interface
2nd to secondary interface (AD =150)
3rd to other router (AD = 151)
In ospf you can advertise default with a route-map that can check the existence of primary interface subnet in Routing table. If present
then announce, otherwise dont.
when primaries are up, 1st default is used. OSPF defaults will be announced but not used
when A primary goes down, it will not generate default but has B's OSPF default and use it
when B primary also go down, then they have no OSPF learned default and they will use their 2nd default
If A's secondary interface also go down then 3rd default will be used
It should work
Zaheer
To Clarify a little more.
>The primary static route used on both the routers (A, B) refer to two links connected to an Upstream ISP within the country. Therefore we intend to push a majority of our Internet traffic through both these circuits. This upstream ISP does not pass internet routes to us as a policy. But we still announce our routes through BGP with an aggregate, & as well as few specific prefixes to also influence the incoming traffic to enter our network via this ISP.
>
>The Secondary static route on both the routers (A, B) refer to two links connected to an Upstream International ISP. We plan to use this bandwidth predominantly for MPLS VPN traffic for a lot International customers, & thereby would prefer to use the circuits, only if the primary links on both the routers are down. I understand this is possible because even if one router's primary link fails, It would use the OSPF propogated default which has a lower administrative distance than the secondary static route configured locally with an administrative distance of 150. Also to mention is the fact that we are not accepting Internet routes sent by the International ISP, because of the need that we need to use the primary links first & only in need of redundancy the International links. Only aggregate routes will be announced upstream via the International provider, affecting the incoming traffic to use these links only when the links to th! e national ISP are down.
>
>But the only concern is that, assume that the primary link on both the routers to the National ISP are down. Then each of the router will start using the default OSPF propogated route sent by the other. The output here would be that router A will send all Internet traffic to router B, which will use its secondary (International link) to forward traffic, & vice versa. In this scenario I would prefer that each router use its locally available secondary circuit if available, thus saving on Inter-POP bandwidth between the two routers, & achieve better load distribution on the International links for outgoing Internet traffic.
>
>Kindly advice on this.. Just assuming on whether some method, wherein administrative distance on the default OSPF routes can be manipulated & increased , or decreased based on the status of the primary link on each router.
>
>Thanks & warm regards,
>Vinod.
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