From: Harindha Fernando (pottaharry@gmail.com)
Date: Tue Jul 08 2008 - 11:19:14 ART
PIM DM Fallback will come into picture if there is no RP available for the
group, isn't it? but if there is a RP then first packets will go via shared
tree and switched to shortest path tree if it finds better path to
source, isn't ? but following the SPT does not mean it is Dense mode, isn't
it?
we can avoid SPT by configuring ip pim spt-threshold infinity so that all
the packets will follow shared tree. but if there is a failure in RP and if
we have not configured no ip pim dm-fallback then it will flood on every
interface if PIM-SM-DM is configured in all the interfaces. but I have a
doubt what will be the case if we have mix of PIM-SM and PIM-SM-DM
interfaces in same PE. will it flood through the PIM-SM interface ? hope not
...
On Tue, Jul 8, 2008 at 5:08 PM, Learn Cisco <cisco.learn@yahoo.com> wrote:
> all sparse mode implementations (sparse-mode + sparse-dense-mode)
> immediately
> revert to a source-based / shortest-path tree after first polling the RP
> for
> the multicast source IP address....unless the spt-threshold is adjusted.
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Harindha Fernando
> Sent: Tuesday,
> July 08, 2008 2:39 AM
> To: John
> Cc: Learn Cisco; ccielab@groupstudy.com
> Subject: Re: Multicast Features
>
> Hi,
>
> If you have configured all the
> interfaces to PIM-SM then fallback mode will
> be sparse , if you have at least
> one interface with SM-DM then
> fallback mode will be Dense, by putting
> no ip pim dm-fallback
> guaranties that fallback will be in Sparse mode.
> Rgds,
> Harri
>
> On Tue, Jul 8, 2008 at 3:31 AM, John <jgarrison1@austin.rr.com>
> wrote:
>
> > spt-threshhold is for source tree. The default is 0 kbs, which
> means that
> > anything over 0 kbs will go to a source tree. no ip pim-dm
> fallback is to
> > prevent, at least sparse-dense mode from falling back to
> dense mode for
> > unknown groups. In the docs I've seen it used in sparse mode
> and
> sometimes
> > not. I'm still trying to find a definitive answer on that.
> Ill probably
> > end up labbing it on friday and then I'll know for sure.
> >
> >
> >
> > "The mind is like a parachute it works best when it's open"
> > ----- Original
> Message ----- From: "Learn Cisco" <cisco.learn@yahoo.com>
> > To:
> <ccielab@groupstudy.com>
> > Cc: <cisco.learn@yahoo.com>
> > Sent: Monday, July
> 07, 2008 5:27 PM
> > Subject: Multicast Features
> >
> >
> >
> > hi, i'm trying to get
> a better grasp on multicast topics. any feedback
> to
> >> the following
> questions would be much appreciated:
> >>
> >> 1.) was wondering if anyone can
> help differentiate between the use of "ip
> >> pim spt-threshold infinity" and
> "no ip pim dm-fallback". they both seem
> to
> >> prevent sparse-dense-mode
> and/or sparse-mode pim from reverting back to a
> >> sourced-tree /
> shortest-path tree unless I'm missing something.
> >>
> >> 2.) would "ip pim
> accept-rp auto-rp" be needed along with one of the cmds
> >> above to ensure no
> spt paths form?
> >>
> >> 3.) when would "ip pim accept-rp x.x.x.x x" be used? i
> guess if i get a
> >> question/requirement that states to have a device accept
> join/prune
> messages
> >> for an rp i'd know to use this feature, but it seems as
> though their
> might
> >> be more to this thing???
> >>
> >> 4.) "ip pim autorp
> listener" is the feature to use when desiring to use
> >> sparse-mode along with
> auto-rp, right? (without statically assigning the
> rp
> >> mapping on all
> sparse-mode devices)
> >>
> >> thanks in advance for any input,
> >>
> >>
> >>
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> >
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