ISDN Backup for OSPF

A client has a Frame-Relay network, Primary PVC's, Backup PVC's and ISDN backup (weighted static routes) are all in Area 0. The main PVC's are all point-to-point sub-interfaces back to their HQ. The routing tables are inefficient.

We are looking into migrating them to MPLS with a separate DMVPN (ADSL) but two of the sites will have ADSL only with ISDN backup due to their small size.The plan is to use and 837 for the remote DMVPN use an existing 2600 router for the remote ISDN backup.

At the HQ my thoughts were:

DMVPN (WAN side) = Area 1 LAN side = Area 0 (to talk to the other HQ routers on the Frame Network in Area 0)

The remote sites 837

DMVPN = Area 1

2600 ISDN Backup Area = 1

A DMVPN in area 1 would surely allow me to run Area 1 as a Totally Stubby area, thus reducing the routing table size on the edge router. I will then run HSRP on the 837 & 2600 and track the ATM interface. Assuming failure I want the ISDN to fire up and dial into the HQ.

My reading suggests that the ISDN at the remote site needs a corresponding Dialler Interface (HQ) in the same Area. If this is the case how would the remote router know to dial the ISDN if the DMVPN fails?

A Totally Stubby Area injects the default route *IA into Area 1. So assuming I have a route on my 837 saying 'ip route BRI_LAN_ROUTER_IP' would this work. I assume that the static default route would only be placed in the routing table if the OSPF injected route fails.



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Darren Green
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check out the Dialer Watch feature

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Thanks for the reply.

I have heard of dialer watch and seen expamples of it used. Never thought to use it though : )



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