From: Kevin Ventra (Kevin_Ventra@xxxxxxxxxxxxxxxxxxx)
Date: Sun Mar 05 2000 - 20:07:53 GMT-3
Looking through various documents I have found,
pg. 780 Routing TCP/IP Vol 1
To prevent route feedback, routes must be filtered as they are incoming
on an interface, before they are entered into the route table.
This implies not to use configurations of the type
distribute-list 3 out ospf 25 (for example)
and use distribute-list 3 int Ethernet 0/1, when performing mutual
redistrbution with OSPF.
Which makes sense because of OSPF Link State Databases.
This I have found was tedious especially if you had multiple loopback
interfaces
and other interfaces. none the less I looks like it will do the job.
pg632 Network design and case studies Second edition details mutual
redistribution using
route maps. I used this approach in one of my labs and it seemed to work
fine for mutual
redistribution of OSPF and EIGRP.
I was wondering if anyone had any comments or preferences to any of these
approaches.
I found it quite interesting that redistributing at the routing process and
not at the
interface level (with OSPF) would cause route feedback (although it makes
perfect sense it was not obvious
at first).
Also any comments on just using distribute list in and not specifying
interfaces or routing processes
and its effects on route feedback ??
-----Original Message-----
From: Jacquie Qi Zhang [mailto:qizhang@cisco.com]
Sent: Sunday, 5 March 2000 13:24
To: Kevin Ventra
Subject: RE: OSPF and distribute list
Chapter "15.3 Mutual Redistribution" in _OSPF DESIGN GUIDE_ at
http://www.cisco.com/warp/public/104/1.html#I00
"Filtering information with link-state protocols such as OSPF is a tricky
business. Distribute-list out works on the ASBR to filter redistributed
routes into other protocols. Distribute-list in works on any router to
prevent routes from being put in the routing table, but it does not prevent
link-state packets from being propagated, downstream routers would still
have the routes. It is better to avoid OSPF filtering as much as possible if
filters can be applied on the other protocols to prevent loops."
Also "Routing TCP/IP Volume I" Chapter 13, Route Filter, Case study: Route
Filtering and Redistribution
Jacquie
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Joshua W. Watkins
Sent: Sunday, March 05, 2000 8:13 AM
To: ccielab@groupstudy.com
Subject: OSPF and distribute list
Can anyone tell me where I might find a sample config of OSPF and
distribute lists? I can't seem to filter a network update using OSPF
to save my life!
Thanks in advance..
josh
Joshua W. Watkins
Systems Engineer
Mountain States Networking
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