From: John Do (mcseccnp03@yahoo.com)
Date: Thu Nov 17 2005 - 00:24:22 GMT-3
Guys,
Let me test my routing skill and give this one a shot. I don't know how this goes but I will give it a try. If there are any errors or mistake please correct me. First of all, multiple points of redistribution just mean that there is more than one redistribution point. For example, redistribution point "A" and redistribution point "B" and so on.
According to the diagram below R2 would not know about the 172.16.2.0 network and R1 would not know about the 172.16.3.0 network. For these two routers to have reach ability to these two networks there must be redistribution on R1 and R2.
R1 would redistribute RIP network into OSPF and R2 would redistribute EIGRP into OSPF. If there is a transit route from OSPF into either RIP or EIGRP then you would also need to redistribute OSPF into both of these protocols. If there is no transit meaning that this a stub end or dead end then what is the point of redistributing OSPF back into both of this routing protocols. I hope that I'm explaining it correctly. If this is still confusing you please take a look at the Netmasterclass website ----> READit------> Public PDF files ------> A Scenario with Multiple Redistribution Points. Lab it up a few times and everything should be aright ;-).
I haven't been working on labs for the past couple months but I will also need to start getting back into it and hopefully next year will be my year. By the way from the diagram below I don't think that there will be any loops in this scenario because is only a one way redistribution point instead of two ways. Well, if there is a need to redistribute OSPF back into the other two protocols then that would consider two way redistribution and of course you would need to filter on R1 and lower the RIP administrative distance for RIP routes. On R2 you would not need to filter or change the administrative distance for EIGRP because external EIGRP routes going into OSPF is a lot higher than OSPF routes.
172.16.2.0 172.16.1.0 172.16.3.0
|-----rip------R1-------ospf------------R2------eigrp------|
Bob Sinclair <bob@bobsinclair.net> wrote:
John,
As a starting point, look for physical loops that cross routing domains. I
have not seen a scenario that risks routing loops in the linear topology you
show, copied below. How would a loop form?
|-----rip------R1-------ospf------------R2------eigrp------|
Bob Sinclair
CCIE #10427, CCSI 30427
www.netmasterclass.net
----- Original Message -----
From: John Matus
To: ccielab@groupstudy.com
Sent: Wednesday, November 16, 2005 8:43 PM
Subject: understading multiple points of redistribution
i'm not sure i'm understanding the whole concept of multile points of
redisribution.
i used to think that this was when there was 2 routers on the same subnet
that were redisributing the same routing protocol to 2 other subnets
|-------eigrp-------R1----------rip---------|
| |
| |
|------eigrp--------R2----------rip---------|
but then i found out that this was not the case and that the following
diagram woujld also clasify as multiple points and that a routing loop
could occur here as well.
|-----rip------R1-------ospf------------R2------eigrp------|
so, technically, does "multiple points of redistribution" just mean that
there are at least 2 routers that are redistributing between 2 protocols
(not necessarily the same 2)?
in that case, i've just done IE's lab 1 and 2, and they don't use any
filters when redistributing, but there are multiple points of
redistribution. should there be filters in place?? were the brains' just
hoping there would be no routing loop, or did they know absolutly that
there was no routing loop by looking at the topology?
what should i be looking for in identifying where a routing loop might
occur? i sure thought i knew, but alas this seems not to be the case.
does it make any difference "where and which" protocols are being
redistributed?........
|--------eigrp---------R1--------ospf------------R2-------------eigrp--|
|--------eigrp---------r1----------ospf-----------R2----------------rip---|
do either of these topologies have any more or less chance of having a
routing loop than the other?
TIA!!!
Regards,
John D. Matus
Technical Support / PAS
Fujitsu Consulting
626-568-7716
John.Matus@tokiom.com
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