Subject: [magma] IGMP snooping and STP

From: [email-masked]
Date: Thu, 14 Oct 2004 16:25:30 -0400

Considerations for IGMP and MLD Snooping Switches says (p5, bottom):

  An IGMP snooping switch should be aware of the
  link layer topology changes caused by Spanning
  Tree operation.  When a port is enabled or
  disabled by Spanning Tree, a General Query may 
  be sent on all active non-router ports...

First, I want to make sure that "enabled" and "disabled" really mean "forwarding" and "blocked" and don't refer to administrative state of the port.  (Perhaps the language in that paragraph could make use of STP terms to be more precise.)

Second, I'm wondering if that includes the initial transition to Up as the switch comes online.  My intuition says it should send queries then but I'm concerned that the list of "active non-router ports" at power up contains all ports.  Is there any problem with (or benefit to) sending queries out ports that have routers?

Thanks for any feedback or insight you can provide.

                              Chris

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From: "Bharani" <[email-masked]>
Date: Fri, 15 Oct 2004 10:52:44 +0530

Hi Chris

Pl find my comments inlined.

Chris: First, I want to make sure that "enabled" and "disabled" really mean
"forwarding" and "blocked" and don't refer to administrative state of port.

Bharani: Yes I feel that it means only "forwarding" and "blocking" and not
admin status, as it is clearly mentioned as "active" non router ports.
(Active - ports in forwarding state in the active topology)

Chris: Second, I'm wondering if that includes the initial transition to Up
as the switch comes online.  My intuition says it should send queries then
but I'm concerned that the list of "active non-router ports" at power up
contains all ports.  Is there any problem with (or benefit to) sending
queries out ports that have routers?

Bharani: In my opinion the snooping switch wont send queries as soon as the
switch comes up. It only forwards the queries that it receives from the
routers, by which it would have also learned router ports.
Once the switch has built a Forwarding Table based on snooped information,
then it sends queries on active non router ports whenever there is a
topology change.
There is no need for a switch to send queries on router ports. It has to
send only to non router ports to which hosts are connected and which intern
will respond to the queries sent by the switch. After wich the newly snooped
information, if any will be updated in the Multicast Forwarding info built
by IGMP Snooping.

Regards
Bharani

***************************************

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
[email-masked]
Sent: Friday, 15 October 2004 1:56 AM
To: [email-masked]
Subject: [magma] IGMP snooping and STP

First, I want to make sure that "enabled" and "disabled" really mean
"forwarding" and "blocked" and don't refer to administrative state of the
port.  (Perhaps the language in that paragraph could make use of STP terms
to be more precise.)

Second, I'm wondering if that includes the initial transition to Up as the
switch comes online.  My intuition says it should send queries then but I'm
concerned that the list of "active non-router ports" at power up contains
all ports.  Is there any problem with (or benefit to) sending queries out
ports that have routers?

                              Chris

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From: "Bharani" <[email-masked]>
Date: Fri, 15 Oct 2004 11:47:45 +0530

Hi Chris

Pl make a note of this point too.

Chris : Second, I'm wondering if that includes the initial transition to Up
as the
switch comes online.  My intuition says it should send queries then but I'm
concerned that the list of "active non-router ports" at power up contains
all ports.  Is there any problem with (or benefit to) sending queries out
ports that have routers?

Bharani: Only when Proxy Reporting feature is supported, then the switch can
send queries by itself on active ports
         when the switch comes online.

Regards
Bharani

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Bharani
Sent: Friday, 15 October 2004 10:53 AM
To: [email-masked]; [email-masked]
Subject: RE: [magma] IGMP snooping and STP

Hi Chris

Regards
Bharani

-----Original Message-----

                              Chris