Software Version sb275a05
19
Version sb275a05
C613-10464-00 Rev H
IGMP Snooping Query Solicitation
(CR00013351)
Query solicitation minimises loss of multicast data after a topology change on
networks that use EPSR or spanning tree (STP, RSTP, or MSTP) for loop
protection and IGMP snooping.
When IGMP snooping is enabled on a VLAN, and EPSR or Spanning Tree (STP,
RSTP, or MSTP) changes the underlying link layer topology of that VLAN, this
can interrupt multicast data flow for a significant length of time. Query
solicitation prevents this by monitoring the VLAN for any topology changes.
When it detects a change, it generates a special IGMP Leave message known as
a Query Solicit, and floods the Query Solicit message to all ports. When the
IGMP Querier receives the message, it responds by sending a General Query.
This refreshes snooped group membership information in the network.
Query solicitation functions by default (without you enabling it) on the root
bridge in an STP topology and the master node in an EPSR topology. By
default, the root bridge or master node always sends a Query Solicit message
when the topology changes.
On other switches in the network, the query solicitation is disabled by default,
but you can enable it by using the command:
set igmpsnooping vlan={
vlan-name
|1..4094|all}
querysolicit={on|yes|true}
If you enable query solicitation on a switch other than the STP root bridge or
EPSR master node, both that switch and the root or master send a Query Solicit
message.
Once the Querier receives the Query Solicit message, it sends out a General
Query and waits for responses, which update the snooping information
throughout the network. If necessary, you can reduce the time this takes by
tuning the IGMP timers, especially the
queryresponseinterval
parameter. For
more information, see the “IGMP Timers and Counters” section of “How To
Configure IGMP on Allied Telesyn Routers and Switches for Multicasting”.
This How To Note is available from
www.alliedtelesyn.co.uk/en-gb/
solutions/techdocs.asp?area=howto
Disabling Query Solicitation and Display Settings
On any switch, you can disable query solicitation by using the command:
set igmpsnooping vlan={
vlan-name
|1..4094|all}
querysolicit={off|no|false}
To see whether query solicitation is on or off, use the command:
show igmpsnooping
Check the new Query Solicitation field, as shown in the following figure.
