Configuring OSPF with NSSA areas for balance an voice traffic

[guigonza]

Hi ...   your help in this case.

I have a network with two principal sites and 70 branch office.  

The connection to branch office is through two providers WAN1 and WAN2.

WAN1 connects branches using OSPF in MPLS L3 and the WAN2 connects branches using L2 connections.  

Just 14 branches has connections to both providers the others are connected only in WAN1.

At the beginning all the branches and sites were in OSPF area 0 in WAN1 and EIGRP in WAN2.

Trying to optimise the routing protocols we suggest to unify to OSPF protocol all the connections.

We can't use EIGRP because the WAN1 provider don't support it and we want to unify to only one routing protocol.

We create an OSPF NSSA area for branches.  

The topology schema is attached in this note.   

We want to unify to OSPF but when we put the branches connections to OSPF area NSSA the branch routers got an default route but the central router got routes using some branch routers to get others …  additional we want to have balance using both connections (WAN1 and WAN2) and we have VoIP and we would like to select the traffic for VoIP through the best link and Data balanced.

I'll Appreciate any suggestion.

[Richard Burts]

I believe that some of what you are experiencing is just in the nature of OSPF as a routing protocol. Am I correct in understanding that you created a single OSPF area for branches? In that case one of the fundamental principles of OSPF is that all routers within an area must have the same understanding of how to reach all network resources within that area. So branches will learn the existence of subnets at other branches and advertise those subnets to other routers. So the central router may well see the subnets at some branches as being reached through other branch routers.

HTH

Rick

[guigonza]

Thanks Richard ...

That's rigth is the OSPF nature.  Is there any suggestions about this configuration to get balance and optimization in WAN routing ?

[Richard Burts]

You have described WAN2 as providing a L2 connection. In this case all of the routers connecting to WAN2 will see all the other WAN2 routers as neighbors connected on the same subnet and in the same area. So they will prefer to reach each others subnets directly rather than going to the principle sites. Perhaps you might want to create an OSPF area to contain the routers connected to WAH2 and a different OSPF area for the other routers.

I am not clear what kind of balancing and what kind of optimization you are trying to achieve. Perhaps you can provide clarification of this?

HTH

Rick