Re: OSPF SHAM-LINK

The whole idea is to make the sham-link preferable.

The existing design is the the sites are in different ospf areas .

like u said, if the ospf routes from both the mpls link and ospf are coming
as IA we can tweak the cost.
That has been done and the routes still prefers to go via the ospf link even
after a very high cost.

--- On Tue, 3/30/10, Joe Astorino <jastorino_at_ipexpert.com> wrote:

From: Joe Astorino <jastorino_at_ipexpert.com>
Subject: Re: OSPF SHAM-LINK
To: "Abiola Jewoola" <biola_y2k_at_yahoo.com>
Cc: "Ahmed Ejaz" <aahmedejaz_at_gmail.com>, ccielab_at_groupstudy.com
Date: Tuesday, March 30, 2010, 3:09 AM

Abiola,

To summarize here -- If you have site 1 and site 2 linked up via MPLS and also
via a backdoor link and both sites are in different areas then there is no
need to use a sham link in the first place. Both the backdoor and mpls routes
will be O IA and you can simply tweak cost.

Now, if you have site 1 and site 2 and they are both in the same area then you
have a problem because the mpls learned routes will still show up as O IA at
best, and the backdoor link will always be preferred. If you are saying that
you have separate sites here then forget about the sham link and lets focus on
manipulating the OSPF cost to get things to route the way you'd like.

On Tue, Mar 30, 2010 at 5:46 AM, Joe Astorino <jastorino_at_ipexpert.com> wrote:

Make both CE sites the same OSPF area

On Tue, Mar 30, 2010 at 5:44 AM, Abiola Jewoola <biola_y2k_at_yahoo.com> wrote:

Yea,

My sham is link up from both sides from the show ip ospf sham-link output a

And full from the show ip ospf nei output!

--- On Tue, 3/30/10, Joe Astorino <jastorino_at_ipexpert.com> wrote:

From: Joe Astorino <jastorino_at_ipexpert.com>
Subject: Re: OSPF SHAM-LINK
To: "Abiola Jewoola" <biola_y2k_at_yahoo.com>

Cc: "Ahmed Ejaz" <aahmedejaz_at_gmail.com>, ccielab_at_groupstudy.com
Date: Tuesday, March 30, 2010, 2:38 AM

Are you sure your sham-link is actually working? It doesn't sound like it
is. If the sham-link was up you would have intra-area O routes here. Take a
look at "sh ip ospf neighbor". Do you see an adjacency over
 the sham-link?

On Tue, Mar 30, 2010 at 3:46 AM, Joe Astorino <jastorino_at_ipexpert.com> wrote:

Post your configurations

On Tue, Mar 30, 2010 at 2:43 AM, Abiola Jewoola <biola_y2k_at_yahoo.com> wrote:

I had already increased the cost of the back door link very high.

Still the ospf is preferring to go through the back door link

--- On Mon, 3/29/10, Joe Astorino <jastorino_at_ipexpert.com> wrote:

From: Joe Astorino <jastorino_at_ipexpert.com>
Subject: Re: OSPF SHAM-LINK
To: "Abiola Jewoola" <biola_y2k_at_yahoo.com>

Cc: "Ahmed Ejaz" <aahmedejaz_at_gmail.com>, ccielab_at_groupstudy.com

Date: Monday, March 29, 2010, 11:10 PM

Ahhh...yes well then that is a different story. Typically we see both
remote sites configured for area 0. In your case if both the backdoor link
and the sham-link learned routes are O IA all you should need to do is tweak

the OSPF metric
 by manipulating cost where necessary. Just remember
that
cost is calculated by adding in the cost of your inbound link.

On Tue, Mar 30, 2010 at 1:39 AM, Abiola Jewoola <biola_y2k_at_yahoo.com> wrote:

>
>
> Find attached the configs on my PE routers.
>
> The process id is the same and i also include the same domain-id . but the
> routes still comes as IA. i guess because the PE routers area pairing with

> CE routers with different areas.
>
>
>
> --- On *Mon, 3/29/10, Ahmed Ejaz <aahmedejaz_at_gmail.com>* wrote:

>

>
> From: Ahmed Ejaz <aahmedejaz_at_gmail.com>
>
 Subject: Re: OSPF SHAM-LINK
> To: "Joe Astorino" <jastorino_at_ipexpert.com>
> Cc: "Abiola Jewoola" <biola_y2k_at_yahoo.com>, ccielab_at_groupstudy.com

> Date: Monday, March 29, 2010, 9:57 PM
>
>
> I guess the ospf process which you are redistributing into bgp requires a
> domain id, that is the reason it is treating it as an IA route. Please add
a

> domain id on both the sides and the routes should come up as O routes
then
> you can modify the cost to not prefer the sham link.
>
> HTH
> Ahmed
>
> On Tue, Mar 30, 2010 at 7:43 AM, Joe Astorino
<jastorino@ipexpert.com<http://mc/compose?to=jastorino@ipexpert.com>
> > wrote:
>
>> OSPF routes coming over the sham-link should be regular O routes
>> (intra-area) and thus should be preferred over O IA routes...post your
>> configurations something does not seem right about that.

>>
>>
>>
>> On Mon, Mar 29, 2010 at 10:35 PM, Abiola Jewoola
<biola_y2k@yahoo.com<http://mc/compose?to=biola_y2k@yahoo.com>>
>> wrote:
>> > Hello G.S
>> >
>> > How can i make ospf prefer to forward route routes via ospf sham-link.
>>
 The
>> > sham link has has a cost of 10 and the routes are coming as IA routes
>> across
>> > the MPLS backbone
>> >
>> > The router is preferring the backdoor link even when i have increased

>> the cost
>> > as high as 65000. The routes are also advertised as IA routes.
>> >
>> > Regards,
>> > Abiola
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net

>> >
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>> >
>> >
>> >
>>
>
>> >
>> >
>>
>>
>>
>> --
>> Regards,
>>
>>
>>
>> Joe Astorino - CCIE #24347
>> Sr. Technical Instructor - IPexpert

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Regards,
Joe Astorino - CCIE #24347
Sr. Technical Instructor - IPexpert
Mailto: jastorino_at_ipexpert.com
Telephone:
 +1.810.326.1444
Live Assistance, Please visit: www.ipexpert.com/chat
eFax: +1.810.454.0130
IPexpert is a premier provider of Self-Study Workbooks, Video on Demand,
Audio Tools, Online Hardware Rental and Classroom Training for the
Cisco
CCIE (R&S, Voice, Security & Service Provider) certification(s) with
training locations throughout the United States, Europe, South Asia and
Australia. Be sure to visit our online communities at
www.ipexpert.com/communities and our public website at www.ipexpert.com
Blogs and organic groups at http://www.ccie.net