[c-nsp] multicast on transit LAN

Marco Regini marco.regini at ascotlc.it
Tue Feb 16 15:19:59 EST 2010

Hi Phil,
I apologize if I'm obscure, and thanks a lot :-) for your patience. 

I have

Layer3/Layer2--Layer3/Layer2 --Layer3/Layer2-- ...

The vlan 100 span the entire chain (the cisco are interconnected via the fc gigabit interface with 802.1q trunk), each node on the chain has a "interface vlan 100" with address on the same network.

The customer, the multicast sender/receiver are on the FastEthernet interfaces, in their dedicated vlan and network.

Regarding Pim Snooping my poor 3560,3750 do not support it, but in the documentation I found again that you need the cisco
be or a router or a switch, not both.

But I'm not an expert so do not trust very much what I say.


-----Original Message-----
From: Phil Mayers [mailto:p.mayers at imperial.ac.uk] 
Sent: martedì 16 febbraio 2010 18:19
To: Marco Regini
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] multicast on transit LAN

On 02/16/2010 04:45 PM, Marco Regini wrote:
> Hi Phil, all my cisco are routing the multicast, the problem is that
> the l3 link between them are not point-to-point.

Understood. You have the config:

layer3 -- layer2 -- (...) -- layer2 -- layer3

...and the multicast needs to pass between the layer3 devices.

The layer3 devices are using PIM to speak to each other, yes?

In which case, you need PIM snooping on the layer2 devices.

What are the layer2 devices? How many are there? Who runs them?

> I tried to enable rgmp,cgmp ... but seems they assumes the apparatus
> being a router or a switch ( if the cisco has a svi on the vlan 100
> it is a router, if not is a switch). I'am not sure if proxing the

I'm sorry, I don't understand you.

RGMP and CGMP are different things, which serve different purposes.

> IGMP will works, because IGMP snooping probably has the same
> limitation, but I want to tray; do you know how to enable it?
> This is a pseudo configuration of apparatus, what lines I need to
> proxy the IGMP arriving to the access interface Fa0/30?

I'm sorry, I don't understand. That configuration cannot possibly work.

Can you give a more detailed configuration?

I've never used IGMP proxy on a cisco, and upon examination it looks 
like it might be a different feature than I thought - the docs seem to 
link it to unidirectional tunnels.

You really need PIM snooping.

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