However, looking at the output below, the OSPF /32 routes are inter-area routes,
so you could probably summarise them back to /24 at the ABR. This would
presumably not be possible in all migration cases (I don't have the time or
inclination to think that theory through right now :-)
Just a thought to throw into the pot.
JMcL
---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 28/09/2000 09:55 am
---------------------------
"Cthulu, CCIE Candidate It's Not Dagon" <[EMAIL PROTECTED]> on
28/09/2000 12:57:07 am
Please respond to "Cthulu, CCIE Candidate It's Not Dagon"
<[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
cc: (bcc: JENNY MCLEOD/NSO/CSDA)
Subject: RE: Migrating from EIGRP to OSPF - Bad News!
The decision process for putting a route in the table is (roughly from my
poor memory so correct at will) is:
1. most specific/longest match
2. AD
3. metrics/cost stuff
4. lunar alignment (just kidding, I forgot this one)
So, since OSPF will always advertise loopbacks with a /32, they will almost
always be inserted in the table even if EIGRP is advertising the same
network and has a lower AD.
HTH,
CHarles
>From: Brian <[EMAIL PROTECTED]>
>To: Chuck Larrieu <[EMAIL PROTECTED]>
>CC: "Cthulu, CCIE Candidate It's Not Dagon" <[EMAIL PROTECTED]>,
> [EMAIL PROTECTED]
>Subject: RE: Migrating from EIGRP to OSPF - Bad News!
>Date: Wed, 27 Sep 2000 08:27:26 -0500 (CDT)
>
>
>The /32's are those the loopbacks?
>
>raising the EIGRP AD should work, it may take some time for the route to
>be invalidated though.
>
>Brian
>
>
>On Tue, 26 Sep 2000, Chuck Larrieu wrote:
>
> > Well, I couldn't resist. I had the router pod set up for a RIP to EIGRP
> > migration test yesterday. I am not sure that the results will soothe
>your
> > concerns, Mr. Cthulu.
> >
> > I would post configurations, but the file size exceeds what Paul
>allows.
> > Those who are interested, contact me off line, and I will send you a
>text
> > file with configurations and routing tables.
> >
> > Following is a routing table resulting from placing OSPF onto a router
> > already running EIGRP. Note that OSPF routes with a mask of /32 are
>being
> > placed into the routing table. I am not sure why this is happening.
>Several
> > tweaks have failed to eliminate these routes. Nor did changing the
>EIGRP
> > distance to 115 ( higher than OSPF's 110 ) eliminate EIGRP routes from
>the
> > routing table.
> >
> > So now I have to wonder what is happening.
> >
> > If no one has a quick and good explanation, I'll try to post configs and
> > fool with this some more. Possibly I can place the routers on line and
>let
> > folks poke around
> >
> > Look forward to some more discussion. Customer visits tomorrow, so I
>won't
> > be back on line until very late in the day.
> >
> > Chuck
> >
> >
> > Router# show ip route
> > Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> > i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
>inter
> > area
> > * - candidate default, U - per-user static route, o - ODR
> > P - periodic downloaded static route
> >
> > Gateway of last resort is not set
> >
> > 192.168.8.0/24 is variably subnetted, 2 subnets, 2 masks
> > D 192.168.8.0/24 [90/2809856] via 192.168.254.5, 23:15:32, Serial1
> > O IA 192.168.8.1/32 [110/129] via 192.168.254.5, 00:05:44, Serial1
> > 192.168.9.0/24 is variably subnetted, 2 subnets, 2 masks
> > O IA 192.168.9.1/32 [110/129] via 192.168.254.5, 00:05:45, Serial1
> > D 192.168.9.0/24 [90/2809856] via 192.168.254.5, 23:15:32, Serial1
> > 192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks
> > D 192.168.10.0/24 [90/2809856] via 192.168.254.5, 23:15:33,
>Serial1
> > O IA 192.168.10.1/32 [110/129] via 192.168.254.5, 00:05:46, Serial1
> > 192.168.11.0/24 is variably subnetted, 2 subnets, 2 masks
> > O IA 192.168.11.1/32 [110/129] via 192.168.254.5, 00:05:46, Serial1
> > D 192.168.11.0/24 [90/2809856] via 192.168.254.5, 23:15:33,
>Serial1
> > 192.168.4.0/24 is variably subnetted, 2 subnets, 2 masks
> > D 192.168.4.0/24 [90/2297856] via 192.168.254.5, 23:15:34, Serial1
> > O IA 192.168.4.1/32 [110/65] via 192.168.254.5, 00:05:47, Serial1
> > 192.168.5.0/24 is variably subnetted, 2 subnets, 2 masks
> > O IA 192.168.5.1/32 [110/65] via 192.168.254.5, 00:05:47, Serial1
> > D 192.168.5.0/24 [90/2297856] via 192.168.254.5, 23:15:34, Serial1
> > 192.168.6.0/24 is variably subnetted, 2 subnets, 2 masks
> > D 192.168.6.0/24 [90/2297856] via 192.168.254.5, 23:15:34, Serial1
> > O IA 192.168.6.1/32 [110/65] via 192.168.254.5, 00:05:47, Serial1
> > 192.168.7.0/24 is variably subnetted, 2 subnets, 2 masks
> > O IA 192.168.7.1/32 [110/65] via 192.168.254.5, 00:05:47, Serial1
> > D 192.168.7.0/24 [90/2297856] via 192.168.254.5, 23:15:34, Serial1
> > C 192.168.0.0/24 is directly connected, Loopback0
> > 192.168.254.0/24 is variably subnetted, 3 subnets, 2 masks
> > C 192.168.254.4/30 is directly connected, Serial1
> > D 192.168.254.0/24 is a summary, 23:15:36, Null0
> > D 192.168.254.0/30 [90/2681856] via 192.168.254.5, 23:15:35,
>Serial1
> > C 192.168.1.0/24 is directly connected, Loopback1
> > C 192.168.2.0/24 is directly connected, Loopback2
> > C 192.168.3.0/24 is directly connected, Loopback3
> > Router#
> > Router#
> >
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
> > Cthulu, CCIE Candidate It's Not Dagon
> > Sent: Tuesday, September 26, 2000 11:29 AM
> > To: [EMAIL PROTECTED]
> > Cc: [EMAIL PROTECTED]
> > Subject: Re: Migrating from EIGRP to OSPF
> >
> > Hey, Brian,
> >
> > Thanks for the info. I have some comments/clarification.
> >
> >
> > >EIGRP carries a lower administrative distance vs. EIGRP.
> > CR: You mean EIGRP (90) has a lower AD than OSPF (110)?
> >
> >
> > So you can
> > >basically turn up OSPF on your routers, and then when it all looks
>kosher,
> > >what I would do is raise the administrative distance of EIGRP above
> > >OSPF..........this will cause the EIGRP routes to phase out and OSPF to
> > >be used. If it all goes crazy........you can revert by simply moving
> > >EIGRP back to the default administrative distance. If you were to have
> > >cleared out your EIGRP config......it would be difficult to put things
> > >back..........
> >
> > CR: That is an excellent suggestion! It would be easy to write a
>script
> > that lower/raise as needed. Thank you!
> >
> >
> > >Ok, why would a more specific route be inserted in OSPF vs. EIGRP? If
>you
> > >deploy your OSPF to match that of your EIGRP, this should not
> > >happen.......its definitly avoidable.
> >
> > CR: I was not clear on this. What I meant to say was that if EIGRP has
>a
> > more specific/longest match route than OSPF (or vice versa), that route
>will
> > be inserted in the routing table rather than the OSPF route. Recalling
>past
> > groupstudy discussions, a learned route gets inserted in the routing
>table
> > in order of preference of:
> >
> > 1. Most specific/longest match
> > 2. administrative distance
> > 3. cost (metrics)
> >
> >
> > I had a situation where a more specific EIGRP route stayed in the
>routing
> > table even though adjustments has been made to prefer OSPF. For example,
>if
> > you enter a network 1.1.1.1 0.0.0.0 area 0 command under OSPF, the mask
>that
> > gets advertised with this route by OSPF is whatever mask you have on the
> > interface. Another thing is that if you advertise loopback interfaces,
>OSPF
> > treats them as stub hosts (with a /32 mask); therfore, the route from
>OSPF
> > will be inserted in the routing table as it is more specific/longest
>match,
> > rather than the same route learned from EIGRP with its lower
>administrative
> > distance. These are the types of problems I want to minimize.
> >
> >
> > Many thanks, Brian, for the suggestions and feedback!
> >
> > Charles
> >
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