From: McLaughlin, Jeffery (JMcLaughlin@sfchronicle.com)
Date: Tue Dec 21 2004 - 03:28:31 GMT-3
Ben,
Let me see if I understand:
1. Hosts on vlan 1 do not support multicast, hence cannot send IGMP joins to
R1 to receive multicast traffic.
2. You are trying to find out if IGMP snooping on the 3550, which has both
vlans 1 and 2 on it, can bypass this problem.
The answer would have to be no. IGMP snooping looks inside IGMP join requests
to determine if a device on a given port is a member of a multicast group.
However, if the devices on vlan 1 do not support multicast, they therefore do
not send IGMP packets, and therefore there is nothing for the switch to snoop.
Enabling multicast routing on the 3550 won't work either. Assuming you have
no layer 3 (SVI) interfaces on the 3550, the "ip multicast-routing" command
will have no effect.
The simplest way to get multicast traffic onto vlan 1 is to use an "ip igmp
join-group x.x.x.x" command under the interface. This, however, requires
statically defining the group, and is not terribly flexible.
Jeff McLaughin
CCIE #14023
-----Original Message-----
From: Lai, Ben [mailto:benlai_cn@hotmail.com]
Sent: Mon 12/20/2004 9:45 PM
To: 'ccie2be'; McLaughlin, Jeffery; 'Sheahan, John'; ccielab@groupstudy.com
Cc:
Subject: RE: When should use IGMP SNOOPING on 3550?
Here's a multicast case;
(VLAN1-E0)-R1----SW(3550)----R2-----R3(E0-VLAN2)
Hosts on vlan1 doesn't support multicast, and they want to gain the
multicast traffice on VLAN2, I enabled pim on the relative interfaces (just
R1, R2&R3), and used the igmp helper-map feature on the Ethernet interface
on both routers ( R1 & R3), I'd like to know, if SW2 doesn't enable
multicast routing, and/or disable igmp snooping, is it work for the hosts on
VLAN1 to gain the multicast traffic on VLAN2?
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: 2004?12?21? 3:22
To: McLaughlin, Jeffery; Sheahan, John; ccielab@groupstudy.com
Subject: Re: When should use IGMP SNOOPING on 3550?
As I recall, the 3550 doesn't support cgmp - at least not in the same way
that Cat 5000's do. Therefore, to restrict mcast traffic to just the ports
that require that traffic, the 3550 has to use igmp snooping.
----- Original Message -----
From: "McLaughlin, Jeffery" <JMcLaughlin@sfchronicle.com>
To: "Sheahan, John" <John.Sheahan@priceline.com>; <ccielab@groupstudy.com>
Sent: Monday, December 20, 2004 12:52 PM
Subject: RE: When should use IGMP SNOOPING on 3550?
> Keep in mind that if the switch doesn't know on which ports multicast
group
> members reside, it has to flood the multicast traffic out every port. One
way
> for the switch to know is to use CGMP, where the router (which is keeping
> track of where IGMP members are) explicitly tells the switch which
multicast
> clients. Another option is for the switch to look inside IGMP packets to
> determine where multicast group members are. Knowing where multicast
group
> members are prevents the switch from having to flood out every port.
>
> Jeff McLaughlin
> CCIE #14023
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Sheahan, John
> Sent: Monday, December 20, 2004 9:40 AM
> To: Brian McGahan; ben; ccielab@groupstudy.com
> Subject: RE: When should use IGMP SNOOPING on 3550?
>
> I guess I don't understand why the switch needs to know..I thought the
> router took care of IGMP joins etc..?
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Brian McGahan
> Sent: Monday, December 20, 2004 11:28 AM
> To: ben; ccielab@groupstudy.com
> Subject: RE: When should use IGMP SNOOPING on 3550?
>
> Ben,
>
> IGMP snooping is used on layer 2 switchports to determine of a
> client located on that port has joined a multicast group. This behavior
> is enabled by default. To view what information is learned via snooping
> issue the "show ip igmp snooping group" command.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
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>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > ben
> > Sent: Sunday, December 19, 2004 9:46 PM
> > To: ccielab@groupstudy.com
> > Subject: When should use IGMP SNOOPING on 3550?
> >
> > In some Multicast cases, it's work that just enable the PIM on the
> > according interface, and configure the appropriate multicast mode, in
> > these cases, It doesn't to enable the IGMP snooping on the 3550
> switch, So
> > I am wondering when should use the IGMP snooping on the switch?
> >
> > Thanks
> >
> >
> _______________________________________________________________________
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