From: Ahmed (ahmed_mustafa01@excite.com)
Date: Fri Nov 28 2003 - 23:59:44 GMT-3
Weidong, Kelly is absolutely right. Weidong, I would refer you to a route redistribution section from a Jeff Doyle's book. He has given some good examples, and has walked through some good examples. --- On Thu 11/27, SMTP Test < kellyrg@bp.com > wrote:From: SMTP Test [mailto: kellyrg@bp.com]To: ahmed_mustafa01@excite.com, ccielab@groupstudy.com, Weidong.Xiao@vi.netDate: Thu, 27 Nov 2003 12:49:24 -0000Subject: RE: multi redistribution between ospf , eigrp , ripv2Will you still not redistribute each protocol back into each other eventhough the admin distance is higher...I believe the routing protocol willstill redistribute the original-eigrp subnets (learned through OSPF )backinto EIGRP (and vica versa)...as it is the OSPF/EIGRP databases that arebeing redistributed...NOT the installed (best route) routingtable........??........This will cause issues.....and more than likelyrouting loops, because, as I understand it, this continually recalculatingof the link state dat!
abase will cause instability....you cannot notnecessarily just rely on admin distances to theorise.I agree Ahmed, you should avoid multi-point two way redistribution if youwant to GUARANTEE network stability.-----Original Message-----From: Weidong Xiao [mailto:Weidong.Xiao@vi.net]Sent: 27 November 2003 09:40To: ahmed_mustafa01@excite.com; ccielab@groupstudy.comSubject: RE: multi redistribution between ospf , eigrp , ripv2Hi Ahmed,Thanks for getting back to me.With respect, I don't agree that routing loop or sub-optimal routing woulddefinetly happen in my topology.Let's say network between R1 and R2 is net12, and net56 is the networkbetween R5 and R6. On R4 under ospf, net12 is imported from eigrp to ospf,and ospf advertise this route (in form of LSA) to the whole ospf domain.When this info arrive R3 via ospf domain, R3 will give route to net12 viaospf domain a distance of 110. At the same time R3 gets route to net12 byeigrp, which give the route a distance of 90, so route t!
o net12 by eigrp isprefered.On R4 under eigrp, net56 is import!
ed from
ospf to eigrp, and eigrp advertisethis route to the whole eigrp domain as an external route. When this infoarrives R3 via eigrp domain, R3 will give route to net56 via eigrp domain adistance of 170. At the same time R3 gets route to net56 by ospf, which givethe route a distance of 110, so route to net56 by ospf is prefered.This logic can go on and on, and I can't see how routing loop would happen.I know that loop busters are tweaking of distance and route-filtering byACL, tagging, and I can use them pretty fast. I just don't think it'snecessary.Come on, CCIEs, double triple quintuple CCIEs, Brian, MADMAN, Scott, Peter,Chuck, Bob,...., come and get me.-----Original Message-----From: Ahmed [mailto:ahmed_mustafa01@excite.com]Sent: 26 November 2003 22:23To: Weidong XiaoSubject: RE: multi redistribution between ospf , eigrp , ripv2Weidoing,Whenever there are multi-point redistribution, routing loop or sub-optimalrouting would definetly happen. In your scenerio, the actual results!
canonly be seen by implementing the Scenerio. There are few options, and theyall depend. You could go with access-lists, distance commands, and routetagging.Regards,Ahmed--- On Wed 11/26, Weidong Xiao < Weidong.Xiao@vi.net > wrote:From: Weidong Xiao [mailto: Weidong.Xiao@vi.net]To: ccielab@groupstudy.comDate: Wed, 26 Nov 2003 13:05:58 -0000Subject: multi redistribution between ospf , eigrp , ripv2R1----R2| || | EIGRPR3----R4 ----------| | OSPF| |R5----R6Hi group,In the above topology, R1, R2, R3 and R4 are running EIGRP, R3, R4, R5 andR6 are running OSPF, R3 and R4 are doing mutual redistribution.Can some guru confirm that without any route filtering, tagging or twistingof distance, routing loop or unoptimal routes will not happen?If this is the case, then if I swap OSPF with RIPv2, or swap EIGRP withRIPv2 (on R3 and R4 set distance of external ospf to 130), no routing loopwill happen even if I do nothing special?Thanks,Weidong________________________________________!
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