From: Geert Nijs (geert.nijs@simac.be)
Date: Thu Aug 24 2006 - 07:35:27 ART
Rick,
Is there only one switch involved ?
If multiple switches are involved connected through L2 links, then IGMP snooping can indeed be a problem, even in one VLAN.
This is because an IGMP snooping enabled switch will "snoop" and actually "capture" an IGMP Membership report.
It will ONLY forward this request on ports it thinks are IGMP router ports. If the switch thinks it does not have any router ports, it will not forward the IGMP Membership report at all and this can generate problems......
More information can be found here: (very nice article, or why multicast can be a pain in the a$$ even in one VLAN :-)
http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml#understand
regards,
Geert
CCIE #13729
________________________________
From: nobody@groupstudy.com on behalf of rick.fox@tcsny.com
Sent: Thu 8/24/2006 0:46
To: Brian McGahan; Rick Fox; ccielab@groupstudy.com
Subject: Re: ICMP snooping on non-routed VLAN
I have a vlan configured on a sup720 without a l3 interface, with servers and receivers sharing that vlan. The hosts do not receive any multicast traffic until I turn off IGMP snooping. I thought it could be a bug, but figured I was forgetting something. Any ideas?
Thanks.
-----Original Message-----
From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
Date: Wed, 23 Aug 2006 17:34:03
To:"Rick Fox" <rick.fox@tcsna.com>,<ccielab@groupstudy.com>
Subject: RE: ICMP snooping on non-routed VLAN
IGMP snooping is a layer 2 function and doesn't require any
layer 3 configuration on the switch performing it. When a host sends an
IGMP join the switch will hear it and add the appropriate multicast MAC
address to the CAM table for that port. What is the specific problem
you are seeing or trying to solve?
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com <http://www.internetworkexpert.com/>
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
24/7 Support: http://forum.internetworkexpert.com <http://forum.internetworkexpert.com/>
Live Chat: http://www.internetworkexpert.com/chat/
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Rick Fox
> Sent: Wednesday, August 23, 2006 11:15 AM
> To: ccielab@groupstudy.com
> Subject: ICMP snooping on non-routed VLAN
>
> Can IGMP work on a vlan without a routed interface?
>
> Lets say you have multiple multicast servers and receivers sharing a
vlan
> that
> is not routed. With IGMP snooping enabled (default), the recievers do
not
> receive any muticast traffic. When IGMP snooping is disabled, the
> receivers
> receive all the multicast traffic. This can be undesirable as the
> receivers
> should only receive multicast on the groups they join.
>
> There is a command IGMP snooping querier, but this requires creating a
> vlan
> interface and putting an ip address on it.
>
> Any other suggestions?
>
> Thanks.
>
>
This archive was generated by hypermail 2.1.4 : Fri Sep 01 2006 - 15:41:58 ART