Re: E1 Vs N OSPF routes

From: Bryan Bartik (bbartik@ipexpert.com)
Date: Sat Mar 14 2009 - 13:30:02 ARST

Hi Guarav,

Not sure I understand, but if you had an NSSA, E routes wouldn't be allowed,
you would only have N routes redistributed by the ASBR. E routes wouldn't
make it in, but the N would be converted to E at the ABR...

Now I guess you could have a scenario where the same route was redistributed
as a N in one nssa area and E in another regular area and they both showed
up at the NSSA ABR like this:

R1 and R4 connected to same LAN 192.168.100.0 (no OSPF on it, just
redistributing)
---R1---R2----R3---R4---

R2(config-router)#do sho ip osp dat | be pe-7
                Type-7 AS External Link States (Area 1)

Link ID ADV Router Age Seq# Checksum Tag
192.168.100.0 1.1.1.1 13 0x80000001 0x000E40 0
<---- From R1 in an NSSA

                Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
192.168.100.0 2.2.2.2 2 0x80000001 0x0084CF 0 <----
Converted to Type 5 by R2
192.168.100.0 4.4.4.4 14 0x80000001 0x006D55 0 <----
From R4 in another area
R2(config-router)#

In this case, the it looks like the same rules would apply as here:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080124c7d.shtml

-hth

On Sat, Mar 14, 2009 at 8:29 AM, GAURAV MADAN <gauravmadan1177@gmail.com>wrote:

> Hi
>
> Can someone cearify the rpeference order that ospf follows while selecting
> between NSSA ; E1 routes (especially when P bit is set ) .
>
> Thnx in advance
> Gaurav Madan
>
>
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-- 
Bryan Bartik
CCIE #23707, CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com

Blogs and organic groups at http://www.ccie.net

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