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Page 77 | AlliedWare™ OS How To Note: IGMP
Configurable IGMP timers and counters > Query Response Interval
Query Response Interval
What this timer does
The Query Response Interval determines the longest time clients can take to reply to a
General Query. The Querier inserts the Query Response Interval into General Query
messages. Clients randomly choose a time between 0 and the Query Response Interval at
which to respond to a General Query. Increasing the Query Response Interval spreads IGMP
messages over a longer time period, which reduces the burstiness of traffic on the network.
The Query Response Interval is also referred to as the Max Response Time in RFC 2236.
It may be useful to decrease the Query Response Interval if you are running EPSR or RSTP.
Decreasing the Query Response Interval reduces the recovery time after a topology change.
For more information, see "Query solicitation (rapid recovery from topology changes)" on
page 26.
Potential problems with changing this timer
If your network has many multicast clients and you make the Query Response Interval too
short, you may congest the Snoopers and Querier with too many Report messages in a short
time.
If you change the Query Response Interval, the Default Timeout Interval also needs to
change, so that clients have an appropriate amount of time to reply to the Query. Since
software versions 28
1
-03 and 2.9.
1
, this happens automatically. For earlier versions, you need
to change it yourself as described on page 82.
How to change this timer
The Query Response Interval is an integer from
1
to 255 in units of 0.
1
seconds, specified
using the queryresponseinterval parameter. The default is
1
00 (
1
0 seconds). The
following example would return a modified Query Response Interval to its default value.
In this example, the Querier sends a General Query every
1
25 seconds. The General Query
contains the Query Response Interval of
1
00, which tells clients that they have
1
0 seconds to
reply to this General Query message.
Manager Switch 1> set ip igmp queryresponseinterval=100
Info (1005003): Operation successful.
Manager Switch 1> show ip igmp
IGMP Protocol
------------------------------------------------------------------------
Status ........................... Enabled
Default Query Interval ........... 125 secs
Default Timeout Interval ......... 260 secs
Last Member Query Interval ....... 10 (1/10secs)
Last Member Query Count .......... 2
Robustness Variable .............. 2
Query Response Interval .......... 100 (1/10secs)
.
.
.