From: Chua, Parry (Parry.Chua@xxxxxxxxxx)
Date: Sun Feb 17 2002 - 01:17:56 GMT-3
There is another issues you should consider, sub-optiomal path. I prefer
the following:-
1. Always ensure that the redistribution metric is higher than the
orginal metric.
2. At the redistribution point, set the AD value of the redistrbuted
route to higer then
it source.(eg assume 172.16.1.0 is source from RIP, set it to 121) if
necessary.
This normally the case of redistribute a higher AD to lower AD
routing protocol.
Regards
Parry
-----Original Message-----
From: Bob Sinclair [mailto:bsin@erols.com]
Sent: Sunday, February 17, 2002 5:41 AM
To: Stephen Oliver
Cc: ccielab@groupstudy.com
Subject: Re: Routing loops.
Steve,
Good suggestion. My guess is mutual redistribution at two points a is
very likely scenario in the lab. Tried this out in my home lab using
OSPF as the backbone and RIP mutually redistributed at two points. Used
the following command under OSFP on the border routers:
distance ospf external 130
Which seemed to work well in this scenario, setting ospf external routes
above RIP's 120. One might consider just lowering the RIP distance
below 110, but this ends up making my RIP area a "transit" area for
backbone traffic.
There is also the ability to set distance for particular routes from
particular route sources as follows:
distance 130 172.16.8.1 0.0.0.0 2
Where 2 is an access-list identifying the routes and 8.1 is a route
source. But I think this latter approach is only good for DV protocols,
including EIGRP, since OSPF does not "get routes" from neighbors.
Thanks for the suggestion. I think I may need this later...
-Bob
----- Original Message -----
From: "Stephen Oliver" <stevie_oliver@hotmail.com>
To: <ccielab@groupstudy.com>
Sent: Saturday, February 16, 2002 1:32 PM
Subject: Routing loops.
> Would anyone like to comment on their methods of stopping routing
loops when
> you have multiple mutual redistribution points in your network.
>
> I try to look at what I will be sending out to another protocol and
build an
> access-list permitting these routes. I use this in a route-map with a
> permit to send the routes to another protocol and in another route-map
to
> allow them to come back into the protocol they originated from but
with a
> higher than default administrative distance. This way if the routes
are
> coming back into the protocol the higher AD ensures if they exist
already in
> say ospf they won't be used unless they disappear from OSPF.
>
> So say I send 125.0.0.0 into eigrp from ospf then at the points where
I
> redistribute into OSPF I manipulate any occurance of this route to
have an
> AD of say 150. If it exists in OSPF the 110 AD is chosen. If it
disappears
> from OSPF and it still comes in via redistribution then it's a valid
> external source and it can still be used with the 150 AD.
>
> Anyone care to comment, criticise or add their opinions.
>
> Stephen
>
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