[c-nsp] OSPF NSSA Question

Jay Hennigan jay at west.net
Mon Oct 4 00:44:39 EDT 2004

On Sun, 3 Oct 2004, Randy Bush wrote:

> > You could try a distribute-list in on each access router limiting
> > it to placing the default and/or your major network(s) into its
> > routing table.  I'm not sure if this would break things, probably
> > best to try it in a lab scenario first.
> and then be surprised to see what it breaks next year.  as you
> said,
> > Because by definition OSPF routers within an area will all have
> > the same link-state database.  Route aggregation is expected to
> > be done between areas.

Yeah, it's one of those areas I'm a little fuzzy on when it comes down
to OSPF internals and Cisco implementation.  I *think* that this is OK
as the low-level OSPF database *should* function according to the spec
and the distribute-list will only determine which of the routes in the
database propagate into the IP routing table.

It would be easy to check with "show ip ospf database" commands on the
various routers with and without the distribute-list.

But, the original poster is proposing 100 routers in the area along with
significant route flaps from customers.  Even if the IP routing table is
nice and tight, there's still quite a bit of low level OSPF churn under
the hood.  Far less of a performance hit than having it affect the routing
table, but still quite a bit of unnecessary noise and processing.

Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
WestNet:  Connecting you to the planet.  805 884-6323      WB6RDV
NetLojix Communications, Inc.  -  http://www.netlojix.com/

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