From: ying chang (ying_c@xxxxxxxxxxx)
Date: Thu May 09 2002 - 11:48:01 GMT-3
Those routes are not directly connected, they are rip routes and showed up
in routing table as 'R' instead of 'C'. The point I'm trying to make is
although both 155.0/24 and 125.0/24 are redistributed from rip processes
into OSPF and becoming the external routes. However, from R3's pespective,
they are a little bit different, because 155.0/24 is also in R3's rip
database, and that's why after "redis ospf ..." into igrp process, you can
only see 125.0/24 but not 155.0/24 in "debug ip igrp tran".
>From: Joe Higgins <netsat@optonline.net>
>To: ying chang <ying_c@hotmail.com>
>CC: ccielab@groupstudy.com
>Subject: Re: Redistribute ospf external route into igrp
>Date: Thu, 09 May 2002 10:02:26 -0400
>
>The way that redistribution appears to work to me is as follows.
>For example if you are redistributing ospf into igrp then on the
>redistribution
>router the IOS looks in its ip routing table and redistributes any routes
>that
>begin with an O in front of it into the igrp process. If you are
>redistributing
>rip into igrp it looks in its routing table and redistributes into igrp any
>routes with an R in front of it. The reason that connected routes in the
>ospf
>database and the rip process do not get redistributed into igrp is because
>they
>have a C (connected) in front of them in the routing table on the
>redistribution
>router. The rule that I use is that if it has a C in front, it is not
>going to
>be redistributed unless you redistribute connected. I welcome any comments
>to
>the contrary.
>
>ying chang wrote:
>
> > Sorry, found a few mistakes from my post below, but the basic concept
> > presented is correct. In short, an external route will not get
>redistributed
> > if it's also an internal route or a local routing process.
> >
> > Chang
> >
> > >From: "ying chang" <ying_c@hotmail.com>
> > >Reply-To: "ying chang" <ying_c@hotmail.com>
> > >To: ccielab@groupstudy.com
> > >Subject: RE: Redistribute ospf external route into igrp
> > >Date: Thu, 09 May 2002 00:32:51 -0400
> > >
> > >After went through a few tests, I don't think the issue is not on
> > >split-horizon but on whose route is more trustworthy:
> > >
> > >Since mutual redistribution is always causing confusion, and this
>problem
> > >can be simulated without mutual redistribution, so I set up an
>environment
> > >like the following:
> > >
> > > R4<--igrp---R3<---rip---R5--172.16.155.0/24
> > > |
> > > ospf
> > > |
> > > R1<--rip----R2--172.16.125.0/24
> > >
> > >and below is what I got:
> > >
> > >Two external routes in R3:
> > >
> > >r3#sio d | b -5 <<<- both 125.0/24 and 155.0/24 are in ospf external db
> > > Type-5 AS External Link States
> > >
> > >Link ID ADV Router Age Seq# Checksum Tag
> > >172.16.125.0 172.16.200.1 48 0x80000001 0xC013 12
> > >172.16.155.0 172.16.146.1 610 0x80000002 0x8E45 35
> > >
> > >Only 172.16.155.0 is redistributed into igrp:
> > >
> > >r3#debug ip igrp tra <<<--sending 125.0/24 but not 155.0/24
> > >IGRP protocol debugging is on
> > >r3#
> > >13:28:22: IGRP: sending update to 255.255.255.255 via Ethernet0
> > >(172.16.52.3)
> > >13:28:22: subnet 172.16.144.0, metric=501
> > >13:28:22: subnet 172.16.145.0, metric=501
> > >13:28:22: subnet 172.16.146.0, metric=501
> > >13:28:22: subnet 172.16.53.0, metric=1100
> > >13:28:22: subnet 172.16.10.0, metric=8476
> > >13:28:22: subnet 172.16.125.0, metric=158250 <<<<----
> > >r3#
> > >r3#sh ip rip data <<<- r3 has 155.0/24 but not 125.0/24
> > >172.16.0.0/16 auto-summary
> > >172.16.145.0/24 directly connected, Loopback1
> > >...
> > >172.16.149.0/24
> > > [1] via 172.16.10.1, 00:00:08, Serial0
> > >172.16.155.0/24 <<<<------
> > > [1] via 172.16.53.1, 00:00:09, Ethernet1
> > >...
> > >r3#
> > >
> > >I think the reason 172.16.155.0/24 was not sending to IGRP is because
>from
> > >R3's point of view, 172.16.155.0/24 is in its rip database (know it by
> > >first
> > >hand), it also knows 172.16.155.0/24 is in ospf - but that's learn from
> > >some
> > >other protocol (second hand stuff), so the route is not cannot be
>trusted,
> > >and that's why when you redistribute ospf into igrp, you only see R1's
>rip
> > >routes but not R4's rip routes. 172.16.125.0/24 did not have this
>problem,
> > >because it's not in R3's local rip database.
> > >
> > >The moral for this problem: when you run more than two protocols in a
> > >router
> > >like this, not only you have to redistribute ospf into igrp, you also
>need
> > >to redistribute directly connected rip routes into igrp.
> > >
> > >Chang
> > >
> > >>From: "Jenkins, Buddy" <buddy.jenkins@csfb.com>
> > >>Reply-To: "Jenkins, Buddy" <buddy.jenkins@csfb.com>
> > >>To: ccielab@groupstudy.com
> > >>Subject: RE: Redistribute ospf external route into igrp
> > >>Date: Thu, 9 May 2002 07:25:00 +0900
> > >>
> > >>Jeff,
> > >>
> > >>Refer to Doyle Volume1 Chapter 11 on redistribution. In the questions
>at
> > >>the end of the chapter there is a question (I don't have the book with
>me
> > >>right now so I can't tell you the specific question) that has the same
> > >>scenario that you have. Doyle says that the reason for that type of
> > >>behaviour is because of the rule of split horizon. This makes sense
>for
> > >>you scanario below because IGRP would use split horizon and OSPF does
>not
> > >>use split horizon. However this is the part that still confuses me.
>I do
> > >>not know why split horizon is applied to a redistribution process. I
> > >>always though split horizon was implemented to not advertise a route
>out
> > >>an
> > >>interface from which that route was learned. Can any of the guru's
>out
> > >>there explain why split horizon is applied during mutual
>redistribution?
> > >>
> > >>Buddy
> > >>
> > >>-----Original Message-----
> > >>From: Jeff Szeto [mailto:jytszeto@hotmail.com]
> > >>Sent: Wednesday, May 08, 2002 5:20 PM
> > >>To: ccielab@groupstudy.com
> > >>Subject: Redistribute ospf external route into igrp
> > >>
> > >>
> > >>Hi,
> > >>
> > >>A router runs IGRP, OSPF and RIP. Mutual redistribution exist between
> > >>OSPF---RIP and OSPF---IGRP. But no redistribution between IGRP and
>RIP.
> > >>From the debug message I found that IGRP is no advertising the RIP
>routes
> > >>that are redistributed into OSPF while the OSPF routes are advertised
> > >>normally.
> > >>On the other hand, the IGRP routes are advertised into RIP through
>OSPF.
> > >>
> > >>Could someone explain the concept behind or point me to a document.
> > >>
> > >>Thanks in advance.
> > >>
> > >>Jeff
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:58:53 GMT-3