From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Wed Oct 02 2002 - 21:09:48 GMT-3
At 9:49 AM +1000 10/3/02, Jason Sinclair wrote:
>I would not call this design as such, however this could be configured via
>the use of two virtual links to area 0 via the other two respective areas.
Mea culpa, Jason. Let me suggest a compromise that does force an ABR
area 0.0.0.0 connection, but doesn't send this traffic over it unless
the primary link fails.
What I usually do in a case like this is define a static route(s)
between the endpoints, give it an administrative distance lower than
OSPF's, and ABSOLUTELY NOT REDISTRIBUTE IT INTO OSPF. That way,
traffic will take the preferred path as long as it's up, but will use
area 0.0.0.0 as backup if there is a primary path failure.
>au
>
> -----Original Message-----
>From: Howard C. Berkowitz [mailto:hcb@gettcomm.com]
>Sent: Thursday, 3 October 2002 04:28
>To: ccielab@groupstudy.com
>Subject: Re: OSPF Design
>
>At 1:51 PM -0400 10/2/02, Peter Wodle wrote:
>>I wonder if the following OSPF Design is valid/workable?
>>
>>Have the area 0 with a no of routers. 1 ABR links area 0 to Area 1.
>>another ABR links area 0 to Area 2. So far no issues. But then we
>>have R12 that connects area 1 & area 2 togather i.e. R12 has one
>>interface in area 1 and one one interface in area 2. R12 has no
>>interface in area 0. So, it is an ABR (right?) but has no link to
>>area 0. Could this could lead to area 1 & area 2 exhange routes via
>>this "backdoor" router?R12
>>
>>Can we do this? I can see it is bad design but...
>
>Not in the present standard or most (if not all) Cisco
>implementations. There is a proposal in the IETF OSPF Working Group
>to do something close to it:
>http://www.ietf.org/internet-drafts/draft-ietf-ospf-mlinks-03.txt
>
>
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