RE: EIGRP IP Default-Network - Confusion Reigns !!!

The post shows that the default-network may be internal or external. It
depends on how it is used. In the article it shows the two ways you use it
and if you look at the output you will see that one way it shows as an EX
route and the other way it shows as an internal, which I thought was your
first question

So both are correct to an extent. The Cisco post should read that it may be
an external route

The flag bit being set to 0x02 will mark the route as a candidate default

http://www.iphelp.ru/faq/21/ch08lev1sec1.html

Regards,

Tyson Scott - CCIE #13513 R&S, Security, and SP

Managing Partner / Sr. Instructor - IPexpert, Inc.

Mailto: <mailto:tscott_at_ipexpert.com> tscott_at_ipexpert.com

From: Ravi Singh [mailto:way2ccie_at_googlemail.com]
Sent: Saturday, December 04, 2010 2:29 PM
To: Tyson Scott
Cc: Cisco certification
Subject: Re: EIGRP IP Default-Network - Confusion Reigns !!!

Hi Tyson,

That post does not actually answer any of the questions, to be
frank.However, I really appreciate your response to this query. Thanks a lot
!!

Regards,
Ravi

On Sat, Dec 4, 2010 at 6:56 PM, Tyson Scott <tscott_at_ipexpert.com> wrote:

Ravi,

Take a look at this blog post,
http://blog.ipexpert.com/2010/03/29/eigrp-ip-default-network-command/, it
should help to answer your questions.

This may also be use for you for other information.
http://www.ipexpert.com/Cisco/CCIE/Library

Regards,
 
Tyson Scott - CCIE #13513 R&S, Security, and SP
Managing Partner / Sr. Instructor - IPexpert, Inc.
Mailto: tscott_at_ipexpert.com

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Ravi
Singh
Sent: Friday, December 03, 2010 11:16 PM
To: Cisco certification
Subject: EIGRP IP Default-Network - Confusion Reigns !!!

Hello All,

We have had numerous discussions on the use of the IP Default-network
command in EIGRP, but I would like to ask a couple of questions which I
couldn't find answers to anywhere on the web.

1) Cisco's documentation and quite a few books say that with EIGRP, the
network which has been configured as the default-network is advertised and
flagged as an external route. Here is a link to the Cisco Doc -

http://www.cisco.com/en/US/docs/ios/iproute_pi/configuration/guide/iri_ip_pr
<http://www.cisco.com/en/US/docs/ios/iproute_pi/configuration/guide/iri_ip_p
r%0Aot_indep_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1056283>

ot_indep_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1056283

This does not seem correct to me . If you read Narbik's puzzles about this
command a couple of weeks back or simply connect two routers back to back
running EIGRP, you would find that the network being advertised as a
candidate-default is being sent and learned as an EIGRP internal route.
Please note that the network is being advertised using the network statement
so i am not talking about routes being genuinely advertised as external
routes using redistribute commands. So the question is- what am I missing
here ?

2) Considering the above is incorrect and the candidate default route can be
an internal route, what bit in the update packet tells the receiving router
that the route is a candidate default. An EIGRP update having an external
TLV contains the Flag field which tells the receiving router whether the
route is supposed to be a candidate default. Doing a packet dissection using
wireshark , I don't seem to find anything in an Internal EIGRP update that
would make the router decide whether to insert the route as a candidate
default or not.

Awaiting your valuable responses !!

Regards,
Ravi

Blogs and organic groups at http://www.ccie.net
Received on Sat Dec 04 2010 - 15:23:26 ART