[c-nsp] multicast on layer 2

[Sam Munzani]

In some cases multicast helps without even IGMP snoop. e.g. you have 
limited WAN bandwidth but not many nodes in LAN that could suffer 
heavily because of flooding all ports.

Sam
> Presence of layer 3 interface on the same VLAN could change the picture.
> Since sources and receivers would register on it enabling PIM could help.
> Could you test it with PIM enabled and let me know whether it helped?
> 
> BTW without IGMP snooping there's no point in using multicast, in fact
> switch will broadcast every multicast frame.
> 
> --
> Jeff Tantsura  CCIE# 11416
> Senior IP Network Engineer
> 
> 
> -----Original Message-----
> From: Andrew K Ho [mailto:aho at yorku.ca] 
> Sent: 27 June 2005 15:28
> To: Tim Stevenson
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] multicast on layer 2
> 
> I'm afraid this setup is just on layer 2.  Two directly connected switches 
> on trunk links, both allowing the same vlan.  Although there is a vlan 
> interface on the router, the traffic shouldn't be processed by the router. 
>  Hence no need for PIM (as Jeff pointed out).  For reasons I can't fathom, 
> IGMP snooping is always off on our network, and as our planners want it to 
> remain this way, the IGMP querier feature would not make any difference.
> 
> Thx for all the replies.
> 
> Andy
> 
> 
> 
> Tim Stevenson <tstevens at cisco.com> 
> 06/24/2005 03:57 PM
> 
> To
> Andrew K Ho <aho at yorku.ca>, cisco-nsp at puck.nether.net
> cc
> 
> Subject
> Re: [c-nsp] multicast on layer 2
> 
> 
> 
> 
> 
> 
> You might try:
> * enabling PIM on an SVI in that VLAN
> * enabling the IGMP querier feature
> * disabling IGMP snooping (not really advisable, floods to all ports)
> 
> For IGMP snooping to work properly, an IGMP querier MUST be present in the 
> 
> VLAN.
> 
> See:
> http://www.cisco.com/warp/public/473/38.html
> 
> HTH,
> Tim
> 
> At 12:28 PM 6/24/2005, Andrew K Ho declared:
> 
>>Hi, I was hoping someone could help me on this.
>>
>>I'm having a problem with an application on our network called Drive 
> 
> Image
> 
>>Pro (used to push pc images to build client machines), which purports to
>>be a multicast application, but which is only being used at layer 2 as 
> 
> all
> 
>>traffic btn server and client  is contained in 1 vlan, hence is working
>>essentially the same as broadcasts.  Howevever, the server and client 
> 
> send
> 
>>multicast packets to a multicast address to send packets.
>>
>>The server is connected to  Model / Serial cisco WS-C6509  OS / Version
>>ios / 12.1(22)E2 on a 100m connection and the client is connected to a
>>100m port on  Model / Serial cisco 4506  OS / Version ios / 12.2(20)EW .
>>They are connected directly through a trunk link, running at gig on 
> 
> fiber.
> 
>> The server and  client are pingable from either side so there is no
>>reachability issue.
>>
>>If the server and client are both on the 4506, it works fine, but won't
>>work if connected as described above.  There are no configs affecting
>>multicast packets.
>>
>>Has anyone come across a problem like this or have any clue as to why it
>>may not be working?
>>
>>Thx in advance
>>
>>Andy
>>_______________________________________________
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> 
> 
> 
> 
> Tim Stevenson, tstevens at cisco.com
> Routing & Switching CCIE #5561
> Technical Marketing Engineer, Catalyst 6500
> Cisco Systems, http://www.cisco.com
> IP Phone: 408-526-6759
> ********************************************************
> The contents of this message may be *Cisco Confidential*
> and are intended for the specified recipients only.
> 
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