From: Nick Shah (nshah@connect.com.au)
Date: Wed Sep 04 2002 - 21:38:41 GMT-3
Further note :
There is this good paper on using distribute lists with DV protocols.
http://www.cisco.com/warp/public/105/34.html
Nick
----- Original Message -----
From: "Hunt Lee" <huntl@webcentral.com.au>
To: <ccielab@groupstudy.com>
Sent: Thursday, September 05, 2002 9:29 AM
Subject: URGENT - Help needed
> Hello Group,
>
> I want to clarify / confirming my understanding regarding filtering
> routes with distribute-lists... and would appreciated if anyone could
> shed some light on this ;)
>
> distribute-list X in - filters routes learned via all incoming
> interfaces from going into the routing table
>
> distribute-list X out - filters any external redistributed routes from
> other protocols.
>
> Ok... as for OSPF:-
>
> distribute-list X in - will still filters routes from all incoming
> interfaces from entering into the routing table. I have read on
> Parkhurst (OSPF Command & Reference) saying that this command can
> filters "O" & "O IA" route, but not "O E2" routes, yet I have also read
> on other books saying that only "O IA" routes can be filtered by this,
> so which is correct?
>
> Also, since OSPF uses LSAs, where OSPF neighbors determines routes from
> the info in the Link State database, this command won't stop the routes
> from going into OSPF Topology database.
>
> distribute-list X in <Serial 0> - same as above, except the filtering
> only applied for routes learned via a specific interface.
>
> distribute-list X out - I have read from different books (as well as
> CCO regarding this). Dr Parkhurst (OSPF Command & Reference) says that
> this command is useless / has no effect on OSPF... yet I have read on
> other sources saying this will still work, where ALL different external
> protocols will be filtered with the list (e.g. if EIGRP & RIP are both
> redistributed into OSPF, then they would both be filtered).
>
> distribute-list X out <rip> - filters only a specific external
> redistributed protocol (O E2) from entering into the ASBR's own OSPF
> database, hence these external routes will be prevented to be
> advertised to the rest of OSPF domain.
>
> ... Apart from those, is it true that I should only use the above 4
> commands from OSPF ABR or OSPF ASBR??
>
> Hunt
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