From: Scott Morris (swm@emanon.com)
Date: Thu Oct 05 2006 - 15:01:01 ART
The "no capability transit" (per the DocCD) forces all packets to go back
through Area 0 routers instead of any shortcuts. (pre v2)
I suppose you could filter the routes anyplace, but you'd need to do a lot
of work looking at your database!
Section 16.3 of RFC2328 (OSPFv2) helps describe some of the calculations
going on.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPExpert VP - Curriculum Development
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
_____
From: LB [mailto:lb.ccie@gmail.com]
Sent: Thursday, October 05, 2006 10:40 AM
To: swm@emanon.com
Cc: WorkerBee; Cisco certification
Subject: Re: OSPFv2 inter-area transit - fundamental concept
So Scott:
If I issue the "no capability transit" command I can have a route through
the trully shortest path? And can I then filter routes etc thru that path?.
Can you point me out to literature on this?
Thanks,
-Leo
On 10/5/06, Scott Morris <swm@emanon.com> wrote:
That won't work. Area 0 is necessary to exchange the LSAs. If you have
only one area, nobody cares what the number is. If you have more than one
area, you MUST have an area 0.
While the packets don't technically have to transit that (not in your
diagram), the LSA exchanges do. Otherwise you make things exponentially
more complex at the database level. :)
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPExpert VP - Curriculum Development
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: WorkerBee [mailto:ciscobee@gmail.com]
Sent: Thursday, October 05, 2006 10:15 AM
To: Scott Morris
Cc: Leo Boulton; Cisco certification
Subject: Re: OSPFv2 inter-area transit - fundamental concept
Hi Scott,
How does it work if I have the following setup where R2 is the ABR without
Area 0?
[R1]----(area 10)-------[R2]------(area 20)-----[R3]
Without Area 0 define in any of R2 interface, R1 and R3 cannot communicate
with each other. "no capability transit" at R2 does not help.
Can you shine some light? :)
On 10/5/06, Scott Morris <swm@emanon.com> wrote:
> OSPFv2 actually allowed a workaround called a transit area, where ospf
> will calculate the truly shortest path. You can turn this off with
> "no capability transit" if you wish.
>
> :)
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@ipexpert.com
> http://www.ipexpert.com <http://www.ipexpert.com>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Leo Boulton
> Sent: Thursday, October 05, 2006 9:01 AM
> To: Cisco certification
> Subject: OSPFv2 inter-area transit - fundamental concept
>
> Hi, and thanks:
>
> Simple question: Is it a restriction of OSPF that all inter-area
> traffic must flow through the backbone area? What if I have two
> non-backbone areas next to each other, does the traffic need to go to
> the backbone and then to the other area? I was always under the
> impression that this was not a requirement of OSPF.
>
> Thanks,
>
> -LB
>
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