[j-nsp] redistribute ospf into ISIS

[Pekka Savola]

On Fri, 18 Apr 2008, Plz wrote:
> Here is the problem,  in my opinion,  when A & B redistribute this ospf
> external route into ISIS, A&B should have this route
> in both OSPF & ISIS,(A advertise this route to B via ISIS, and B advertise
> this route to A in ISIS).
> The fact is not this.
> When i show route on A, i find 1 route in OSPF, and another in ISIS(B
> advertise to A). But only the ospf route is found on B.
> Seems that A didn't advertise this route 1.1.1.1/32 to B. This route (
> 1.1.1.1/32) was redistribute into ISIS on A coz i
> find it in the A's ISIS database. Wat's more,  A didn't advertise this route
> to the uplink router either.
>
> Could anyone explain this? Any advise ll be appreciated.

The default OSPF preferences are better than IS-IS.  IS-IS doesn't 
redistribute a route that isn't active.  Also, if you receive an IS-IS 
route with (say) metric 10, and your IS-IS redistribution policy were 
to set your advertised metric to 15, no redistribution occurs because 
IS-IS already has a better route.

If you had this problem with BGP advertisements, "advertise-inactive" 
would help you; in this case it doesn't.  You should probably look at 
the metrics of IS-IS routes and possibly routing protocol preferences 
(e.g. make IS-IS preferred over OSPF).

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings