I have two sites that currently have connectivity via a DS3, and I'm about to add secondary connectivity via a service provider MPLS network. I've asked the SP about the new service, and for all intents and purposes, I'm receiving a 40Mb layer 2 link between my two sites.
I currently have OSPF running on my Multi-layer switches at each site, and on the DS3 routers in between. I'm planning on changing the DS3 so it's in Area 0, changing my Multi-layer switches so they act as ABR's and have seperate area's for each site.
Would you recommend leaving the DS3 routers in Area 0, with their internal interfaces in the same subnet as the WAN side of the multi-layer switches? Or should I use a different subnet for the MLS-DS3 Router connection?
Also, is there any way to "trick" OSPF into load-balancing across the DS3 and the 40Mb VPLS network?
Thanks in advance,
you can use a subnet in the same IP block for the new link and keep the DS3 links and the MPLS links in area 0.
If you do so you can achieve load balancing if desired.
you need to think on how OSPF metric calculation works.
Use the point of view of the multilayer switch: it has a LAN link to the WAN router and then there is the DS3 link.
When enabling the MPLS link I suppose you con nect directly the multilayer switches at the two sites. If so without any change the new link become the primary path for its lower metric.
In order to load balance use ip ospf cost under the L3 link to MPLS service and use a cost value = cost from L3 switch to WAN router + cost of DS3
typically the first is 1 and the second is int (100/44) with default reference BW in OSPF.
Notice that DS3 bandwidth is more then 40 Mbps. (something less 44)
Hope to help