Configuring Igmp Query And Response Parameters - HP 4800G Series Configuration Manual

Configuring IGMP packet options on an interface
Follow these steps to configure IGMP packet options on an interface:
To do...
Enter system view
Enter interface view
Configure the interface to
discard any IGMP message
that does not carry the
Router-Alert option
Enable insertion of the
Router-Alert option into IGMP
messages

Configuring IGMP Query and Response Parameters

On startup, the IGMP querier sends "startup query count" IGMP general queries at the "startup query
interval", which is 1/4 of the "IGMP query interval".
The IGMP querier periodically sends IGMP general queries at the "IGMP query interval" to determine
whether any multicast group member exists on the network. You can tune the IGMP general query
interval based on actual condition of the network.
Upon receiving an IGMP leave message, the IGMP querier sends "last member query count" IGMP
group-specific queries at the "IGMP last member query interval". IGMP is robust to "robustness variable
minus 1" packet losses on a network. Therefore, a greater value of the robustness variable makes the
IGMP querier "more robust", but results in a longer multicast group timeout time.
Upon receiving an IGMP query (general query or group-specific query), a host starts a delay timer for
each multicast group it has joined. This timer is initialized to a random value in the range of 0 to the
maximum response time, which is derived from the Max Response Time field in the IGMP query. When
the timer value comes down to 0, the host sends an IGMP report to the corresponding multicast group.
An appropriate setting of the maximum response time for IGMP queries allows hosts to respond to
queries quickly and avoids bursts of IGMP traffic on the network caused by reports simultaneously sent
by a large number of hosts when the corresponding timers expires simultaneously.
For IGMP general queries, you can configure the maximum response time to fill their Max
Response time field.
For IGMP group-specific queries, you can configure the IGMP last member query interval to fill
their Max Response time field. Namely, for IGMP group-specific queries, the maximum response
time equals the IGMP last member query interval.
When multiple multicast routers exist on the same subnet, the IGMP querier is responsible for sending
IGMP queries. If a non-querier router receives no IGMP query from the querier within the "other querier
present interval", it will assume the querier to have expired and a new querier election process is
launched; otherwise, the non-querier router will reset its "other querier present timer".
Configuring IGMP query and response parameters globally
Follow these steps to configure IGMP query and response parameters globally:
Use the command...
system-view
interface interface-type
interface-number
igmp require-router-alert
igmp send-router-alert
1-13
Remarks
—
—
Optional
By default, the device does not
check the Router-Alert option.
Optional
By default, IGMP messages
carry the Router-Alert option.