From: Scott Morris (smorris@ipexpert.com)
Date: Fri Oct 19 2007 - 01:04:36 ART
According to your drawing though, that meant that the method a packet would
use to cross one place or another could not traverse from/to every single
link within Area 1 alone. That constitutes a discontiguous area.
If you had made one of the sides an area 2, I think things would have been
fine.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
smorris@ipexpert.com
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
http://www.ipexpert.com
_____
From: James MacDonald [mailto:j4m3sm63@yahoo.ca]
Sent: Thursday, October 18, 2007 10:27 PM
To: smorris@ipexpert.com; ccielab@groupstudy.com
Subject: Re: OSPF - area design question
I think what I was looking for was an idea of what constitutes a
discontigous area. In my example I had a regular router in area1 only ...
connected with 2 PTP links back to 2 separate ABRs ... each link a different
cost. The ABRs were connected together with only a single link in area0 ...
in my lab routing was not working properly. I.e. ABR1 saw paths to the area
router via it's link at cost 40 and ABR2 only saw it's own path to the area
router at the cost of 80 (those were my set costs) ... it should see the
path via ABR1 as better but it wasn't.
When i enabled a new link between the ABR's in area1 then it worked
properly.
Hope this makes sense the way i describe ... i'm a bit burnt out at the
moment :)
Thanks
------------------------------
Jim MacDonald
j4m3sm63@yahoo.ca
------------------------------
----- Original Message ----
From: Scott Morris <smorris@ipexpert.com>
To: James MacDonald <j4m3sm63@yahoo.ca>; ccielab@groupstudy.com
Sent: Thursday, October 18, 2007 9:58:21 PM
Subject: RE: OSPF - area design question
Per your other e-mail, I don't think it has anything to do with a "worthy"
question or not, just that ASCII art is scary. :)
In any event, I'm not sure what your basic question here actually is. If
you are looking as to whether this is a valid network design or not, the
short answer is no. Per OSPF RFC, everyone inside an area must have an
identical database for that area. Having ANY discontiguous area screws that
up.
We can fix that with tunnels or virtual links, but that doesn't make it a
good idea!
The whole point of an area is an addressing hierarchy, which theorhetically
gives us the ability to aggregate/summarize our routes for more efficient
routing. If you start band-aiding things together, you'll slowly degrade
that idea to where it just plain doesn't work.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
James MacDonald
Sent: Monday, October 15, 2007 10:05 PM
To: ccielab@groupstudy.com
Subject: OSPF - area design question
In an environment with 2 core routers in ospf area 0 connected back-to-back
... and a distribution router in a separate area connected to both cores
with PTP links ... do i need another link between the cores within the same
regional area for continuity of the area??? The ASCII art version of the
network would be like this:
_area1_ RTR1 _area1_
/
\
/ \
C1 ----- area 0 ------ C2
so do I need this?
_area1_ RTR1 _area1_
/
\
/ \
C1 \ ----- area 0 ----- /
C2
\----- area 1 ------/
Hope this makes sense ... my formatting may mess up in email ...
Thanks,
------------------------------
Jim MacDonald
j4m3sm63@yahoo.ca
------------------------------
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This archive was generated by hypermail 2.1.4 : Fri Nov 16 2007 - 13:11:17 ART