Re: IE Workbook lab 3 Task 2.1 and 4.1

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Thanks
Larry Hadrava
CCIE #12203
Check Out MyBlog: http://ccie12203.wordpress.com/

On Tue, Jun 15, 2010 at 8:57 AM, Anthony Sequeira <asequeira_at_ine.com> wrote:

> Hi Antonio! (Great name by the way!)
>
> The issue here stems from the use of OSPF as the IGP on the PEs. The
> loopbacks possess a /24 mask. The PE generates the implicit NULL, but for
> the /24 connected prefix. The /32 bit OSPF network type loopback
> advertisement will be untagged on the adjacent devices.
>
> We solve this issue in this case through the requirement of a /32 bit mask
> configured on the PE loopbacks.
>
> You were correct in that the Deep Dive author was referring to the implicit
> NULL as the special label.
>
> Great work and continue to enjoy your studies!
>
> On Jun 15, 2010, at 5:00 AM, Antonio Saez wrote:
>
> > Hi Anthony,
> >
> > Could you explain this deeper?
> > The NULL label advertised for the /32 prefix I suppose is the PHP
> implicit
> > null. If true, is not advertised for a non /32 prefix?
> > What is the special label you refer?
> >
> > Regards and thank you in advance
> >
> >
> > -----Mensaje original-----
> > De: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] En nombre de
> > Anthony Sequeira
> > Enviado el: martes, 15 de junio de 2010 6:08
> > Para: Julio Carrasco
> > CC: ccielab_at_groupstudy.com
> > Asunto: Re: IE Workbook lab 3 Task 2.1 and 4.1
> >
> > Hello Julio!
> >
> > Without the task in front of me, I am going to guess that R4 and R5 are
> PE
> > routers in an MPLS L3 VPN scenario. To quote a "Deep Dive" from the very
> > latest version of our WB II....
> >
> > "The use of a /32 prefix allows the local router to advertise a NULL
> label
> > for the prefix. Any non-host route will generate a special label that the
> > local router will use to perform an aggregate lookup based on the
> > destination IP address in the packet. With the NULL label advertisement,
> the
> > label lookup will be performed based on the VPNv4 label, in the case of
> an
> > MPLS VPN scenario."
> >
> > Warmest Regards,
> >
> > Anthony J. Sequeira, CCIE #15626
> > Senior CCIE Instructor
> >
> > Test your Tier 1 Knowledge
> > Q: For RIPng, you can only disable split-horizon ...
> > A: globally
> > More Info: http://www.ietf.org/rfc/rfc2080.txt
> >
> > On Jun 14, 2010, at 10:19 AM, Julio Carrasco wrote:
> >
> >> Hello experts,
> >> I am reviewing this lab, and I saw, that on Task 2.1 it says that is
> > necessay
> >> for Lo0 on R4 and R5, to be announced with a mask of 32 bits, so the LDP
> >> peering on task 4.1 needs both loopbacks to be a /32 mask.
> >> I do not understand exactly why, so could anyone please help me with
> that
> > ?
> >>
> >> Thanks in advance and best regards !!!!
> >>
> >>
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Received on Tue Jun 15 2010 - 09:30:45 ART