RE: ip multicast

From: Standley, Jeffrey (jeffrey.standley@shawgrp.com)
Date: Thu Dec 14 2006 - 20:27:15 ART

Thanks Rajan...exactly what I was looking for!

According to the Command Reference at
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hi
mc_r/mlt_i2h.htm#wp1081469

...the default on the routers is for "a multicast group in the absence
of rendezvous point (RP) information will fall to dense mode, regardless
of the interface mode configuration"

The way I read this is that even if you have the interface configured as
sparse-mode, if there is no RP present, either statically configured or
through auto-rp, the router wills fallback to dense-mode for the group.

Appears that the "no ip pim dm-fallback" command will override this
default and prevent the router from going into dense-mode. Looks like
it would need to be configured on all routers that have auto-rp and no
static rp's, but would not be needed on Routers that have static rp's
configured as they would not fallback to dense-mode.

Thanks again for the information!

Jeff Standley

Network Engineer (CCNP, CCSP)

The Shaw Group, Inc.

4171 Essen Lane

Baton Rouge, LA 70809

Tele: (225) 987-6209

Jeffrey.Standley@Shawgrp.com

Global Help Desk <http://servicedesk.shawgrp.com/>

________________________________

From: Rajan kumaresan [mailto:rajankumaresan@gmail.com]
Sent: Thursday, December 14, 2006 1:44 AM
To: Salman Abbas
Cc: Standley, Jeffrey; a_sadki1@hotmail.com; ccielab@groupstudy.com
Subject: Re: ip multicast

May be no densemode fallback is the extra command ???.But I have few
clarifications..

<http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/h
imc_c/chap05/mcbbasic.htm#wp1134342>

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hi
mc_c/chap05/mcbbasic.htm#wp1134342
<http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/h
imc_c/chap05/mcbbasic.htm#wp1134342>

From the above link, for the below task,

* sparse-mode, Auto-RP and ip pim autorp listener --> has been
configured on one router ( say R1) which is also RP and Mapping
Agent.Configuring " no ip pim dm-fallback" makes sense here right?

What about the other Multicast routers ( Non RP & Non Mapping Agent)
with sparse-mode & ip pim autorp listener enabled.Do you really
require "no ip pim dm-fallback.

Configuring *ONLY* on R1 will not surve the purpose ? OR Is it like "
no dense-mode fallback" has to be configured "wherever ip pim autorp
listener" is configured ?

Note: As per doccd no ip pim dm-fallback --> (optional) Prevents PIM
dense mode fallback. * Configure this command on all routers in a PIM
sparse-mode domain

Static RP :

There is a example for sparse-mode with single static RP.Why no
densemode fall back (no ip pim dm-fallback) is needed for the interface
which has only sparse mode configured and also eventhen only static RP
is available.I hope some one can clarify me..

Thanks,

Rajan

On 12/13/06, Salman Abbas <dukelondon@gmail.com> wrote:

No, nothing else needs to be configured.

On 12/14/06, Standley, Jeffrey < jeffrey.standley@shawgrp.com
<mailto:jeffrey.standley@shawgrp.com> > wrote:
>
> If all interfaces are running in sparse-mode and I want to use
auto-rp, is
> their anything extra that needs to be configured other than "ip pim
autorp
> listener"?
>
> Jeff Standley
> Network Engineer (CCNP, CCSP)
> The Shaw Group, Inc.
> 4171 Essen Ln
> Baton Rouge, LA 70809
> 225.987.6209
>
> ----- Original Message -----
> From: nobody@groupstudy.com <nobody@groupstudy.com>
> To: Abderrahim sadki < a_sadki1@hotmail.com
<mailto:a_sadki1@hotmail.com> >
> Cc: ccielab@groupstudy.com <ccielab@groupstudy.com
<mailto:ccielab@groupstudy..com> >
> Sent: Wed Dec 13 08:46:41 2006
> Subject: Re: ip multicast
>
> Hi bro,
>
> If you want to configure auto-rp, you MUST use sparse-dense mode as
you
> need
> dense mode for groups 224.0..1.39 <http://224.0.1.39> and 224.0.1.40.
However, if the question
> explicity prohibits the use of sparse-dense mode, you will have to use
> sparse mode with "ip pim autorp listener" on all multicast running
> routers.
>
> HTH,
>
> Cheers!!
> Salman
>
>
>
> On 12/13/06, Abderrahim sadki <a_sadki1@hotmail.com> wrote:
> >
> > Hi,
> >
> > How can I know f I need to use sparse-dense mode or sparse mode
only??
> >
> > Knowing that I will have to configure autp-rp.
> >
> > Thanks
> >
> > --------------------------------------------------------------------
> >
> > From: Ivan <ivan@iip.net>
> > Reply-To: Ivan < ivan@iip.net>
> > To: ccielab@groupstudy.com, JB <jellyboy@gmail.com>
> > Subject: Re: As-path Q ^ and _
> > Date: Wed, 13 Dec 2006 12:02:37 +0300
> > >^100$ - it is your direct peer
> > >_100$ - prefix originated in AS100
> > >
> > > > Hi Group, I am wanting to know the difference between the
> > following 2
> > > > expressions. I have included what I think are the correct
> > > > interpretations. Please expand upon if I am incorrect....
> > > >
> > > >
> > > > ^100$ routes that originated in AS100 only (and that is the only
> > AS)
> > > > _100$ routes that originated in AS100 (and there may be other
> > ASes
> > > > prepended to this)
> > > >
> > > > I have had a play on looking glass and those were my
> > conclusions....
> > > >
> > > >
> > > > TIA,
> > > >
> > > > JB
> > > >
> > > >
> >

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