From: Carl Willias (mandingo2073@yahoo.com)
Date: Fri Oct 14 2005 - 23:17:50 GMT-3
Landon
I think you could have used the distance command on both R3 and R4. Set OSPF adminstrative distance to be 171 just for the routes in question. Then EIGRP external routes would be preferred over the OSPF routes.
Also by using a distribute list in you are not keeping the route advertisements from coming into the LSA database you are only keeping them out of the routing table this could lead to sub optimal routing.
CW
----- Original Message ----
From: Landon Fitts <lafitts@cisco.com>
To: Victor Cappuccio <cvictor@protokolgroup.com>
Cc: ccielab@groupstudy.com
Sent: Friday, October 14, 2005 20:13:15
Subject: RE: EIGRP - OSPF Redistribution
Ok. I was able to get tagging using route-map and distribute-list
to work with the configurations below on both R3 and R4:
---------------------------------------------------
router ospf 1
redistribute eigrp 1 subnets route-map tag-eigrp
distribute-list route-map block-eigrp in
!
access-list 7 permit x.x.x.x
!
route-map block-eigrp deny 10
match tag 7
route-map block-eigrp permit 20
!
route-map tag-eigrp permit 10
match ip address 7
set tag 7
route-map tag-eigrp permit 20
------------------------------------------------------
Using just a "distribute-list in" also works, and is less
configuration:
router ospf 1
redistribute eigrp 1 subnets
distribute-list 7 in
!
access-list 7 deny x.x.x.x
access-list 7 permit any
- Landon
_____
From: Victor Cappuccio [mailto:cvictor@protokolgroup.com]
Sent: Friday, October 14, 2005 8:58 PM
To: lafitts@cisco.com
Cc: ccielab@groupstudy.com
Subject: Re: EIGRP - OSPF Redistribution
Landon,
Ok let me see if I get the picture here..
When you redistribute in R4 to OSPF you are going to have an external (e2,
e1) ospf route that you can TAG.
This route is learnt by R3 via OSPF and EIGRP.. but by means of the AD then
the route is going to be preferred via OSPF write?
If this is ok for you, then why not filtering at R3 using the TAG that R4
set (or viceversas)?
also comes into my mind that I you can filter by means of the tag in the
mutual redistribution process at R3 and R4, also you can filter by the type
of the route that is external, Let me know your opinion..
Thanks for the clarification
Victor
Landon Fitts wrote:
Victor,
Yes, that is correct R3,R4, and R2 are in AS-1 running EIGRP.
Also, R2 is in AS-2 running EIGRP with R1. The problem is how to
prevent R3 and R4 from installing the redistributed AS-2 EIGRP
routes in their routing table. The reason being is if this
happens you will get a routing loop for the routes learned from
AS-2, because R3 and R4 see the AS-2 routes as EIGRP External,
and also sees those same routes via OSPF as OSPF External. You
would want the path to networks in AS-2 to be via R2, but it will
take the OSPF route via R5, because of the lower admin distance.
Does that make sense? I used a "distribute-list in" under OSPF
process at R3 and R4 for the AS-2 networks and that worked, but
I wanted to know of any other methods. I tried using tags, but
could not get that to work.
I think my topology diagram got a bit jumbled. Here it is again:
|-----R3-----|
R1-----R2------| |-----R5
|-----R4-----|
Regards,
Landon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Victor Cappuccio
Sent: Friday, October 14, 2005 8:26 PM
To: Landon Fitts
Subject: Re: EIGRP - OSPF Redistribution
Hello Ladon, nice question to think about. Could you please can you clarify
a little bit the problem R3, R3 and R4 are running EIGRP AS-1 between them
??
- R1 and R2 are running EIGRP AS-2 between them
- R3, R3, and R4 are running EIGRP AS-1 between them
- R3, R4, and R5 are running OSPF AREA-0 over FR between them
- R2 is mutually redistributing EIGRP AS-1 & AS-2
- R3 and R4 are mutually redistributing OSPF and EIGRP
Do not get the topology yet
My first thought are tags (but could you please clarify the problem) Thanks
Victor.
Landon Fitts wrote:
I have a question on the various methods available to prevent EIGRP
routes that are redistributed into OSPF at two different ASBRs from
being installed into the route table of those same ABSRs when relearned
>from OSPF. I was able to use a "distribute-list <acl> in" under the
ospf process to successfully achieve this, but I couldn't get it to
work using a route-map on the redistribution statement matching on the
tagged eigrp networks. Using the route-map with tagging method, the
routing table would go back and forth between installing an E2 route
and a EX route on the ASBRs every time I cleared the route table.
To make this clearer below is my topology:
|---R3-----|
R1-----R2-----SW-----| |-----R5
<mailto:lafitts@cisco.com> <mailto:lafitts@cisco.com>
|---R4-----|
Scenario:
- R1 and R2 are running EIGRP AS-2 between them
- R3, R3, and R4 are running EIGRP AS-1 between them
- R3, R4, and R5 are running OSPF AREA-0 over FR between them
- R2 is mutually redistributing EIGRP AS-1 & AS-2
- R3 and R4 are mutually redistributing OSPF and EIGRP
Problem:
Networks from AS-2 will be seen as EIGRP external routes at R3 & R4, so
when these networks are relearned back from R5 via OSPF the route table
at R3 and R4 will install the E2 routes because of the lower admin
distance. This will not be a problem for the networks learned from
AS-1 via R2, because at R3 & R4 those networks will be seen as internal
EIGRP routes.
Route Redistribution at multiple redistribution points has never been
an easy topic for me, but this scenario seems to add more
complications. Can any of you routing experts shed some light on this
for me?
Thanks,
Landon
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