Hi!

Am 10.12.2013 um 10:14 schrieb Mark Tinka <mark.ti...@seacom.mu>:
> "passive-interface" in IS-IS basically means:
> 
>       - If an interface is defined as passive.
>       - Advertise whatever IP address is on it.
>       - But don't run IS-IS on it.

Yep. That sums it up quite nicely, which is why I’m citing it just this once 
more.

In OSPF it is the same *if* the connected prefix is part of the
„network“ statement in your OSPF process. Which is the „traditional“
way of setting up an OSPF domain if you follow Moy et al.

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.

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 ;-)

Thanks
Patrick
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