RE: (*,G) entries upstream of the RP in sparse mode

Hello Ovidiu,

In sparse mode in Cisco IOS the (*,G) entry is created when:

        1. a router receives an IGMP membership report from a client or a
PIM join message from a downstream router
        2. a multicast stream is detected and (S,G) state must be created

The exception is source specific multicast, in which no (*,G) state is
maintained.

As you suggest, the (*,G) shared tree is not used to distribute traffic
between the source and the RP and is unnecessary.

The (*,G) entry is not used to distribute traffic in dense mode; it is
simply a parent data structure for the (S,G), so I do not believe it is
related to dense mode fallback.

HTH,

Bob Sinclair CCIE 10427 CCSI 30427
CIERS2 Online Instructor
www.tinyurl.com/ciers2online

> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Ovidiu Neghina
> Sent: Saturday, August 21, 2010 6:46 AM
> To: Cisco certification; Cisco certification
> Subject: (*,G) entries upstream of the RP in sparse mode
>
> Hi
> I have a short question.
> we have a sparse mode scenario with static RP - R3 with this topology
> from antonio soares lab:
> http://ccie18473.net/dynamips/dynamips.htm#pim-sm
> Topology is : Source-R1-R2-R3-R4-R5-Receiver
> Why do we have on R1, and R2 (*,G ) entries when sending traffic from
> the source ? I know that is normal to have it dowstream of the RP but
> i don't understand whey we have it upstream of the RP ? Is it for
> dense mode fallback ?
>
> R1#sh ip mroute 224.1.1.1
> (*, 224.1.1.1), 00:00:26/stopped, RP 3.3.3.3, flags: SPF
> Incoming interface: Serial1/1, RPF nbr 12.12.12.2
> Outgoing interface list: Null
> (10.10.10.1, 224.1.1.1), 00:00:26/00:03:28, flags: FT
> Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0
> Outgoing interface list:
> Serial1/1, Forward/Sparse, 00:00:26/00:03:04
>
> br
> Ovidiu
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.851 / Virus Database: 271.1.1/3084 - Release Date:
> 08/20/10 14:35:00

Blogs and organic groups at http://www.ccie.net
Received on Sat Aug 21 2010 - 11:45:09 ART