ProCurve 2610-PWR Technical Information download pdf (Page 106)

Multimedia Traffic Control with IP Multicast (IGMP)

Using the Switch as Querier

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 the Command Prompt to disable the Querier

capability for that VLAN.

Note A Querier is required for proper IGMP operation. For this reason, if you disable

the Querier function on a 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

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ProCurve 2610-PWR Technical Information Page 106