[nsp] Re: Redistributing static subnets via separate OSPF process

[Gert Doering]

Hi,

On Sun, Oct 05, 2003 at 08:57:12PM -0500, Robert A. Hayden wrote:
> 
> > Actually I think the problem is "it won't redistribute a route that is 
> > not actually being *used*" - so when you do "redistribute OSPF", it will
> > pick up all OSPF routes that are currently also in the main routing
> > table (due to best administrative distance).  Which is not the case here,
> > because those prefixes are already there as a static.
> 
> However, you can specify the specific OSPF process to redistribute, 

Yes, but...

> so why
> would it pick up everything in the table?

... the generic redistribution rule is "redistribute only best path
routes" (to avoid loops).

I'm not 100 per cent sure whether that's the issue here - haven't done
something like this before - but that's what usually bites people that
have a mixture of BGP and static routes.

[ example ]

> In the above example, I'd expect ospf 15 to announce 10.0.1.0 and quash 
> (via the distribute list) 0.0.0.0.  Then, OSPF 10 will pass the 
> announcement to 10.0.1.0 to everyone talking on that process.  Of course, 
> this is what I expect.  Obviously, it ain't working like that and I have a 
> sense I'm just not groking something really simple.

OSPF 10 will take OSPF 15's routes only if those routes are, at the same
time, the *best* routes to that prefix.  As there is a static route as
well, which has better administrative distance, OSPF 15's routes are not
"better", and won't be used.

> I like to use separate OSPF process for various customers on the network
> that I exchange routes with (this is a university backbone, btw).  This
> allows me to tweak each ones' distribute lists and routing session as
> needed and then tell OSPF 10 to redistribute their specific process back 
> to the backbone.

That's a useful approach - just don't do it for the statics.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
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