On Tuesday, December 10, 2013 11:41:10 AM Patrick M. Hausen 
wrote:

> Most ISPs I know who run OSPF configure it the way I
> described with very narrow „network“ statements and
> explicit redistribution. Essentially my subscriber lines
> are from the IGP’s point of view not part of my AS and
> every router running subscriber lines is an ASBR. The
> prefixes are consecutively injected as AS external LSAs.

I find all these knobs relatively complicated for an IGP. 
But, I can see how enterprise network would need them, 
although such networks have also started migrating to the 
service provider way of doing things.

> BTW: this is the only way (as far as I know) how you
> *can* filter what goes in your link state database and
> what doesn’t. Despite the „traditional“ literature
> claiming that you cannot do that with OSPF at all. Which
> is of course correct but for AS external LSAs ;-)

BGP just gives you more control, and as your network grows, 
BGP scales better than an IGP. Look at the state of the 
Internet routing table :-).

Mark.

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