From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Thu Sep 08 2005 - 08:56:05 GMT-3
I am told there is no "Cisco way" for filtering routes. What the
proctors look for is routes in the routing table and a method of
achieving connectivity that does not violate any conditions of a
question. If the question does not forbid tags, route-maps, distribute
lists etc. you are free to use them as long as you keep to the
constraints of the question and the solution works.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Rajib Khan
Sent: Thursday, September 08, 2005 6:22 AM
To: ccielab@groupstudy.com
Subject: Re: route feedback and cisco way
Thanks for every ones reply
Would follwoing mutual re-distribution be Cisco way and would filter
route feedback
router rip
redistribut ospf 10 match internal external-1 external-2 metric 5
route-map ospftorip
Router ospf 10
redistiribute rip subnets met 120 route-map riptoospf
route-map riptoospf den 10
match tag 10
route-map riptoospf per 20
set tag 20
route-map ospftorip de 10
match tag 20
route-map ospftorip per 20
set tag 10
Counld any one please help me with this.
Thanks in advance
Raj
Godswill Oletu <oletu@inbox.lv> wrote:
Raj,
As per the default behaviour of both routing protocols, yes there is the
risk of running into routing loops. All RIP routes have an AD of 120 and
OSPF 90, though in OSPF, redistributed routes will be flaged O E2 or O
N2 by default, but they will have the same AD of 90 with internal
routes. For RIP, everybody will go by the same name 'R' with an AD of
120.
There are gzallion ways to solve this problem, it will depend on your
situation and what you are asked to do or not to do: The few I can
remember
include:
1. Use tags to filter routes.
2. Assign a higher AD to all external OSPF routes (distance osfp
.......).
3. Redistribute into OSPF using O E1/O N1 instead of the defaults (this
will ensure that external path cost are accounted for).
4. Assign a higher AD to all routes that originates from the RIP domain
(distance 121 .....) 5. Manipulate the default metric of redistributed
routes to make them less desirable.
6. Use offset-list in RIP to increase the hops of redistributed routes.
7. Use of distribute-list
8. etc! etc!! etc!!!
If not restricted by your scenerio, you best shot is to use option 1
above to eliminate the loops at the source. The other methods do not
eliminate the source of the loop, but only help you to manipulate and
manage the situation so that, despite the fact that they may appear to
be some routes that would have lead to loops in the routing database,
you have been able to ensure that they never appear in the routing
table. Option 1 will make sure that, those routes never made it to the
routing database in the first place.
HTH
----- Original Message -----
From: "Rajib Khan"
To:
Sent: Wednesday, September 07, 2005 6:12 AM
Subject: route feedback
> Hi there,
>
> Are there any route feedback risk while redistributing between RIP and
> OSPF
>
> Thanks in advance
>
> Raj
>
>
>
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