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Enhancements in Release F.02.02
Operation and Enhancements for Multimedia Traffic Control (IGMP)
Querier Operation
The function of the IGMP Querier is to poll other IGMP-enabled devices in an IGMP-enabled VLAN
to elicit group membership information. The switch performs this function if there is no other device
in the VLAN, such as a multicast router, to act as Querier. Although the switch automatically ceases
Querier operation in an IGMP-enabled VLAN if it detects another Querier on the VLAN, you can also
use a CLI command to disable the Querier function for that VLAN. For example, to disable the Querier
function on VLAN 1 in a Series 2500 switch:
HP2512(config)# no vlan 1 ip igmp querier Disables Querier function on VLAN 1.
HP2512(vlan-1)# no ip igmp querier Disables Querier function on VLAN 1
from within the VLAN 1 context.
Note
A Querier is required for proper IGMP operation. For this reason, if you disable the Querier function
on a Series 2500 switch, ensure that there is an IGMP Querier (and, preferably, a backup Querier)
available on the same VLAN.
If the switch becomes the Querier for a particular VLAN (for example, the DEFAULT_VLAN), then
subsequently detects queries transmitted from another device on the same VLAN, the switch ceases
to operate as the Querier for that VLAN. If this occurs, the switch Event Log lists a pair of messages
similar to these:
I 01/15/01 09:01:13 igmp: DEFAULT_VLAN: Other Querier detected
I 01/15/01 09:01:13 igmp: DEFAULT_VLAN: This switch is no longer Querier
In the above scenario, if the other device ceases to operate as a Querier on the default VLAN, then
the switch detects this change and can become the Querier as long as it is not pre-empted by some
other IGMP Querier on the VLAN. In this case, the switch Event Log lists messages similar to the
following to indicate that the switch has become the Querier on the VLAN:
I 01/15/01 09:21:55 igmp: DEFAULT_VLAN: Querier Election in process
I 01/15/01 09:22:00 igmp: DEFAULT_VLAN: This switch has been elected as
Querier