RE: switch in the mcast tree

Whenever a switch receives a Pim hello on its port it makes that port
the mrouter port and add that port in the forwarding list of IGMP
snooping database.

Here is a good link which explains what needs to be done in such
scenarios:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note
09186a008059a9df.shtml

/Ruchir

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Joe Astorino
Sent: Tuesday, December 29, 2009 7:08 AM
To: Keegan.Holley_at_sungard.com
Cc: Bryan Bartik; Bit Gossip; ccielab; nobody_at_groupstudy.com
Subject: Re: switch in the mcast tree

Weather you have traffic or not, you are still going to have PIM hello
messages sent on each segment you are running PIM. This is a separate
function.

On Mon, Dec 28, 2009 at 8:27 PM, <Keegan.Holley_at_sungard.com> wrote:

> Also, the routers will have to send join messages for traffic to be
sent
> from the RP (sparse) in the first place so snooping PIM hellos only
> applies to dense mode traffic. In the second example the multicast
> traffic is encapsulated in unicast (register messages) and sent to the
RP
> so the switch would not cause an issue their either.
>
>
>
> From:
> Bryan Bartik <bbartik_at_ipexpert.com>
> To:
> Bit Gossip <bit.gossip_at_chello.nl>
> Cc:
> ccielab <ccielab_at_groupstudy.com>
> Date:
> 12/28/2009 05:06 PM
> Subject:
> Re: switch in the mcast tree
> Sent by:
> <nobody_at_groupstudy.com>
>
>
>
> Snooping is done on IGMP and PIM by default. The following excerpt is
> from:
>
>
>
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/relea
se/12
>
> .2_35_se/configuration/guide/swigmp.html#wp1025709
>
> "Multicast-capable router ports are added to the forwarding table for
> every
> Layer 2 multicast entry. The switch learns of such ports through one
of
> these methods:
>
> Snooping on IGMP queries, Protocol Independent Multicast (PIM)
packets,
> and
> Distance Vector Multicast Routing Protocol (DVMRP) packets "
>
> -hth
>
> On Mon, Dec 28, 2009 at 3:36 PM, Bit Gossip <bit.gossip_at_chello.nl>
wrote:
>
> > Experts,
> > if there is a switch, let's say Cat3750 between the last hop router
and
> > the mcast receiver, the switch snoops igmp by default and based on
that
> > knows on which ports to forward mcast frames; that is clear.
> > But let's say that the switch is between two mcast routers of the
mcast
> > tree, or between the source and the first-hop router, then there is
no
> > IGMP to snoop. How does it behave then?
> > - floods mcast frame towards all ports as if it was bcast
> > - doesn't forward mcast at all
> > - something else
> >
> > Thanks a lot,
> > Bit.
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> >
Received on Tue Dec 29 2009 - 09:29:03 ART