From: James MacDonald (j4m3sm63@yahoo.ca)
Date: Thu Oct 18 2007 - 23:27:24 ART
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!
smorris@ipexpert.com
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 - 13:11:16 ART