[c-nsp] Need help with setting up ip multicastrouting

[Rob Taylor]

On 10/13/2010 3:41 AM, Phil Mayers wrote:
> On 10/13/2010 08:37 AM, Gert Doering wrote:
>> Hi,
>>
>> On Wed, Oct 13, 2010 at 08:18:47AM +0100, Phil Mayers wrote:
>>> On 10/12/2010 09:46 PM, Gert Doering wrote:
>>>> On Tue, Oct 12, 2010 at 02:59:28PM -0500, 
>>>> Christopher.Marget at usc-bt.com
>>>> wrote:
>>>>> The switch listens to the following messages in order to detect 
>>>>> router
>>>>> ports with IGMP snooping:
>>>>> · IGMP Membership query send to 01?00?5e?00?00?01
>>>>> · PIMv1 hello send to 01?00?5e?00?00?02
>>>>> · PIMv2 hello send to 01?00?5e?00?00?0d
>>>>> · DVMRP probes send to 01?00?5e?00?04
>>>>> · MOSPF message send to 01?00?5e?00?05 or 06
>>>>
>>>> Thanks for clarifying this.  Indeed, with this information, IGMP 
>>>> snooping
>>>> should never be harmful for router-switch-router traffic.
>>>
>>> That is not my experience.
>>
>> Can you share details?
>
> Sorry, I did realise after sending that it was too terse to be useful.
>
> Essentially I've observed exactly the behaviour you described in a 
> previous email. Two PIM routers either side of a layer2 switch would 
> fail to pass any routed multicast traffic because IGMP snooping was 
> enabled and was "eating" it. PIM snooping was the solution I decided I 
> needed, but it was easier to just remove the switch and go for a 
> direct link in that case.
>
> Now I must admit: when I think about it, I don't know what model the 
> layer2 switch in question was; it may not even have been a Cisco (this 
> was some time back) in which case Christopher may also be right ;o)

Christopher is right here ... in this case, even with l2 switch in 
between, the mrouter ports should receive all mcast presented to the 
vlan, as well as any igmp group members on that vlan as well.