[nsp] OSPF Area Design

Matthew Crocker matthew at crocker.com
Wed Feb 25 18:20:45 EST 2004

Are the routers that connect the frame network to the offices also the 
ones that handle the direct Inet links?  Or, do you have 2 routers in 
each office?  I would set the frame-relay network as area 0 and create 
a different area for each office.


  Office A:
   has internet connection on router R.A1
   has frame connection on router R.A2
   has LAN segment

Office B:
   has internet connection on R.B2
   has frame connection on router R.B2
   has LAN segment

  Main Office
   has Internet connection on R.M1
   has frame connection on route R.M2
   has T1 to data center 1 on router R.M3
   has T1 to data center 2 on router R.M4
   has LAN segment

  Datacenter 1
    has T1 to main office on router R.D1
    has T1 to datacenter 2 on router R.D2
    has LAN segment

OSPF area 0 contains R.A2, R.B2, R.M2,   PVCs interfaces on all routers 
listen for OSPF from all other routers (full mesh)
OSPF area contains R.A1, R.A2
OSPF area contains R.B1, R.B2
OSPF area contains R.M1, R.M2, R.M3, R.M4
OSPF area contains R.D1, R.D2

router R.A1 originates default 0/0
router R.B1 originates default 0/0
router R.M1 originates default 0/0

On Feb 25, 2004, at 5:15 PM, Vandy Hamidi wrote:

> Current State:
>  -4 Remote offices
> 	-3 have dedicated Internet
>  -1 Main Office
> 	-Offices fully meshed through Frame-Relay
> 	-Has dedicated INet
>  -2 Remote Data Centers
> 	-Data Centers fully meshed with Main office
> We're Configuring OSPF for our 4 remote and Main offices using 
> Frame-Relay to fully mesh all locations.
> Our main office also has a fully meshed point-to-point network with 
> our 2 data centers.
> We'll have 4 connections to the internet from our 5 offices and we'd 
> like to be able to provide (originate 0/0) internet access to all 
> offices (current and new) as a backup for those that have dedicated 
> Inet and primary for offices w/o dedicated Inet.
> All offices need to communicate directly with each other over the WAN.
> We're currently using Static routes, but want to move to dynamic 
> routing for resiliency and ease of scalability.  We chose OSPF because 
> it's compatible with our Cisco and non-Cisco equipment.
> What's the best way to design the OSPF Areas that will give us the 
> most effective routing and resiliency to failures while still 
> maintaining a simple configuration?
> 	-=Vandy=-
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