[Xorp-users] Example config files for connecting different OSPF areas?

[Kristian Larsson]

On Wed, Dec 05, 2007 at 04:21:38PM -0800, Ben Greear wrote:
> Kristian Larsson wrote:
> 
>> It's basically the same as with only one area..
>> with the exception that you have more than one
>> area ;)
>> Have you run into any problems?
> 
> Ok, this is probably another basic misunderstanding of OSPF on my part:
> 
> I have router 1, with 2 interfaces: 10.3.0.1/24, 10.3.1.5/24 and area 
> 0.0.0.1
> A third interface is in area 0.0.0.0
> That interface connects to router 2, which in turn connects to
> router 3.  All interfaces in R2, R3 are area 0.0.0.0
> 
> I was hoping that the routing table for R2 would
> show something like:
> 
> 10.3.0.0/16 via 10.0.0.1 dev rddVR1  proto xorp  metric 2 notify
> 
> (ie, consolidate the two 10.3 subnets into a single route).

Okey, yes, this is not how areas work. Areas are
simply to limit the scope of an SPF calculation.
Routes from one (normal) area to another (normal)
area is distributed as an external route.

I'm not certain about XORP, but Cisco provides
functionality to aggregate prefixes into larger
ones, but it's not completely automatic, you still
have to specify the aggregates by hand.

Stubby areas usually just contain a default from
the ABR(s).


> Instead, I see:
> 
> 10.3.0.0/24 via 10.0.0.1 dev rddVR1  proto xorp  metric 2 notify
> 10.3.1.0/24 via 10.0.0.1 dev rddVR1  proto xorp  metric 2 notify
> 
> 
> Now, after a bit more thinking..this sounds like it couldn't really
> work since there may be other 10.3.x.x subnets elsewhere.  But, is there
> a way to somehow tell it that we have all 10.3.x.x/24 subnets on or
> behind R1 so that only the 10.3.0.0/16 route is propagated to the
> rest of the OSPF network?

Dunno about XORP ;)

  -K

-- 
Kristian Larsson                                        KLL-RIPE
Network Engineer & Peering Coordinator      SpriteLink [AS39525]
+46 704 910401			              kll at spritelink.net