RE: OSPF SHAM LINKS

Dears,
I tried the scenario several times on GNS and here is the result:
SHAM LINK is needed to prefer MPBGP cloud over backdoor, whether its Intra or
INTER AREA!!
Why?
- Without sham link we will have 2 Inter area route, one through MPLS and one
through backdoor, it willalways prefer the backdoor link since it is coming
from area 0 between backdoor link.
When you create shamlink, MPLS clound will also become backbone 0 and then it
will look at OSPF cost (don't forget to create virtual link for discontiguous
area 0)
Br,Hussam
> From: ricardo7632003_at_hotmail.com
> To: hussamkibbi_at_hotmail.com; narbikk_at_gmail.com
> CC: ccielab_at_groupstudy.com
> Subject: RE: OSPF SHAM LINKS
> Date: Thu, 3 Feb 2011 22:04:30 -0300
>
> A sham link is required only between two VPN sites that belong to the same
> area and have the backdoor link for backup needs
>
>
> Ricardo
>
> > From: hussamkibbi_at_hotmail.com
> > To: narbikk_at_gmail.com
> > CC: ccielab_at_groupstudy.com
> > Subject: RE: OSPF SHAM LINKS
> > Date: Fri, 4 Feb 2011 00:48:45 +0000
> >
> > Thank you all for the valuable information.But my question is: Do we need
> Sham
> > link if we already have inter-area:
> >
> > R1---MPBGP--------R2
> > | | | |OSPF Area 1
> > OSPF Area 2 | | |
> |R3--Ospf
> > area 0----R4
> >
> > I tried scenario above on GNS and I didn't see any difference, before and
> > after using sham links.R4 can see R3 through mpls as Inter-area without
> sham
> > links.
> > So do we need it here for any reason?maybe as design for super backbone
> area
> > 0?
> >
> >
> >
> >
> > > Date: Thu, 3 Feb 2011 11:37:15 -0800
> > > Subject: Re: OSPF SHAM LINKS
> > > From: narbikk_at_gmail.com
> > > To: hussamkibbi_at_hotmail.com
> > > CC: ccielab_at_groupstudy.com
> > >
> > > Just to add to whats been said here....
> > > You could actually configure Sham-link for back door and GRE through
the
> > > cloud for "O" routes, these are some of your options, it all depends
what
> > > you like to do.
> > >
> > > On Thu, Feb 3, 2011 at 9:18 AM, Hussam EL Kebbi
> > <hussamkibbi_at_hotmail.com>wrote:
> > >
> > > > Hi Experts,
> > > > Do we need Sham-links between OSPF Inter area (then MPBGP) having
same
> > > > domain-id?
> > > > or it is only needed to keep the intra area routes as Intra area
> routes?
> > > >
> > > > Thanks,
> > > >
> > > >
> > > > Blogs and organic groups at http://www.ccie.net
> > > >
> > > >
Received on Fri Feb 04 2011 - 14:48:50 ART