From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Tue Feb 18 2003 - 16:27:23 GMT-3
I agree that whenever there is more than one OSPF Area, if those areas are
to propagate routes to one another (using OSPF LSA propagation) an OSPF area
0 (0.0.0.0) is needed. Each of the areas must have an ABR. An ABR has one
interface in OSPF area 0 (0.0.0.0).
If there is only one area and no expected growth, the OSPF area used can be
anything. (You probably wouldn't want to use OSPF in this scenario.)
Another scenarion that wouldn't be used but is functionally possible is
redistributing between OPSF areas. If an area 0 is not used, routes can be
shared between two (or more) OSPF non-zero areas using redistribution. This
is not propagating OSPF LSA'a between areas (the redistributed routes are
LSA type 5's in the new area(s)so it doesn't really qualify as OSPF where
the interarea LSA's would be type 3.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
mdye@bevillcntr.org
Sent: Monday, February 17, 2003 3:23 PM
To: Joe; 'Mark Miller'; 'Sam Munzani'; ccielab@groupstudy.com
Cc: cciesecurity@yahoogroups.com
Subject: RE: Can you have OSPF without area 0 at all?
I agree with Joe. OSPF has full knowledge of Area 0 being the backbone. All
OSPF implementations must have an area 0.
The current RFC for OSPF (2328) says:
" 3.1. The backbone of the Autonomous System
The OSPF backbone is the special OSPF Area 0 (often written as
Area 0.0.0.0, since OSPF Area ID's are typically formatted as IP
addresses). The OSPF backbone always contains all area border
routers. The backbone is responsible for distributing routing
information between non-backbone areas. The backbone must be
contiguous. However, it need not be physically contiguous;
backbone connectivity can be established/maintained through the
configuration of virtual links.
"
Mark Dye
At 02:34 PM 2/17/03 -0500, Joe wrote:
>Please send us the link you refer to. I have to say that this is simply
>not true. You will ONLY send routes from your area, whatever it may be,
>into area 0, the backbone, so you can't just arbitrarily designate any
>area as the backbone. It MUST be area 0.
>
>Joe
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Mark Miller
>Sent: Friday, February 14, 2003 6:15 PM
>To: Sam Munzani; ccielab@groupstudy.com
>Cc: cciesecurity@yahoogroups.com
>Subject: Re: Can you have OSPF without area 0 at all?
>
>
>The routing process in ospf has no concept that "area 0" is the backbone
>area. You can make it any number you want. I remember reading
>something on this. I'll try to dig it up and send you a link.
>
>Mark Miller
>
>
>----- Original Message -----
>From: "Sam Munzani" <sam@munzani.com>
>To: <ccielab@groupstudy.com>
>Cc: <cciesecurity@yahoogroups.com>
>Sent: Friday, February 14, 2003 12:56 PM
>Subject: Can you have OSPF without area 0 at all?
>
>
>> Team,
>>
>> I came across an interesting finding. I want to take everybody's
>> opinion
>on this before putting anything in production. We are building an OSPF
>network that will eventually merge with company's main OSPF backbone
>network. The core group has assigned us ospf area number 555.
>>
>> When I configure all my routers with OSPF area 555(with no area 0 at
>> all),
>it seems to be building up routing table. I always thought OSPF needs
>area 0 to function. Will this work of we add a non cisco device with
>area 555 configuration?
>>
>> What is the catch 22 in this configuration? I have started reading
>> OSPF
>RFC to figure out all technical details.
>>
>> Thanks,
>> Sam Munzani
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