RE: OSPF Problem

hi,
Dear all
Sham link and virtual are both Virtual in natures, but they work in
differently.
i hope you know about virutal links already .
Sham link is related to MPLS concept.
where you have to 2 x CE and connected to and 2 x PE. OSPF is PE - CE
protocols running between PE and CE as well.
What happens in this case if you are running OSPF across on the CE as well
just to use the Backup?
you can't use MPLS links across for this site, Reason
Intraarea (o) is prefer over Interarea (IA), this means that MPLS can't be
used
because when we redistribute OSPF into BGP and from BGP back to OSPF they
appear on the other side as IA, but if site has same routes via Intraarea (o)
it would prefer the others link and not the IA routes (MPLS)
but our requirement is to use MPLS across.
here we make sham link across 2 PE, and this way we make sure that site use
MPLS and not the directly connected links.
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t8/feature/guide/ospfshmk.html
so the only in Sham links they prefer IA routes over O roues.
i hope that would be helpful
mazhar
CCIE (RS & SP)

> Date: Tue, 5 Jul 2011 21:26:53 +0530
> Subject: Re: OSPF Problem
> From: routingfreak_at_gmail.com
> To: bhmccie_at_gmail.com
> CC: ccielab_at_groupstudy.com
>
> hmm Thanks Hammer for ur valuable info
>
> I m looking for some GREAT's response
>
> On Tue, Jul 5, 2011 at 9:23 PM, -Hammer- <bhmccie_at_gmail.com> wrote:
>
> > **
> > There are certainly more qualified folks here that may speak up but I do
> > not look at it as extending a non backbone link. I look at it as a method
to
> > enforce more preferred (the cloud) routing between PEs. I look at it more
or
> > less as a pvc or a tunnel between the PEs. I'm sure that's not the best
way
> > but it works for me to think thru it.
> >
> > -Hammer-
> >
> > "I was a normal American nerd"
> > -Jack Herer
> >
> >
> >
> > On 07/05/2011 10:48 AM, Routing Freak wrote:
> >
> > Hey Hammer, Good one
> >
> > But stilll I hava a problem, Is sham link extending ur non backbone link
to
> > the backbone link ( ie ur Super Backbone)
> >
> >
> > On Tue, Jul 5, 2011 at 9:12 PM, -Hammer- <bhmccie_at_gmail.com> wrote:
> >
> >> Dude I didn't mean to simplify it. You were asking for the difference
> >> and I thought a clearer explanation might have helped. I don't look at
these
> >> as being in the same realm and that's why maybe I am missing where you
are
> >> confused. Yes, V-Links are an "extension" of area 0. Whereas sham links
are
> >> used to "bridge" together multiple PEs in the same MPLS VPN backbone.
The
> >> sham link gets you past the default OSPF rules for selecting intra-area
> >> routes instead of inter-area. The sham link also allows the sites to
> >> communicate over the MPLS VPN instead of via any external paths not
provided
> >> via the cloud. Does that help?
> >>
> >> -Hammer-
> >>
> >> "I was a normal American nerd"
> >> -Jack Herer
> >>
> >>
> >>
> >>
> >> On 07/05/2011 10:33 AM, Routing Freak wrote:
> >>
> >> Dude i know how to configure ospf sham link . I need to know about the
> >> difference technically speaking differences
> >>
> >> Share some theory behind both, What r the similarities and what r the
> >> differences?
> >>
> >>
> >> On Tue, Jul 5, 2011 at 8:55 PM, -Hammer- <bhmccie_at_gmail.com> wrote:
> >>
> >>> This helped me understand sham links better a while back....
> >>>
> >>> http://blog.ipexpert.com/2010/01/20/introduction-to-ospf-sham-link/
> >>>
> >>> -Hammer-
> >>>
> >>> "I was a normal American nerd"
> >>> -Jack Herer
> >>>
> >>>
> >>>
> >>> On 07/05/2011 10:17 AM, Routing Freak wrote:
> >>> > Hey mates,
> >>> > I have a little confusion. What is the difference between Sham link
and
> >>> > Virtual Link?
> >>> >
> >>> > I know that Virtual Link is to extend ur backbone
> >>> > Sham link is used as a false link between two PE's . Is it extending
> >>> ur
> >>> > Area to other area and fool them that they r in the same area??
> >>> >
> >>> > Because Sham link mainly used as a virtual cable which sends Intra
area
> >>> > LSA's ( which is the Type 1 LSA's) to other PE .
> >>> >
> >>> > What does exactly the difference betwen Virtual links and Sham links
> >>> >
> >>> >
> >>> > Blogs and organic groups at http://www.ccie.net
> >>> >
> >>> >
Received on Tue Jul 05 2011 - 17:22:44 ART