Would you guys cut it out!!!!!
Now I've got another lab idea to try out, to whit: if you install OSPF over
EIGRP, what will the OSPF side of things look like? I.e. the spf tables? I
am confident in predicting that the routing table will contain only the
EIGRP routes, because those would be preferred due to lower admin distance.
( all other things being equal )
Such a lab would, of course, be of little practical use. Just another
distraction to satisfy my idle curiosity.
Geez, this will be another late night on the routers, I can tell.
Chuck
-----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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