Configuring Igmp Query And Response Parameters - HP A6600 Configuration Manual

To do...
3. Configure the interface to
discard any IGMP message
that does not carry the
Router-Alert option.
4. Enable insertion of the
Router-Alert option into IGMP
messages.

Configuring IGMP query and response parameters

The IGMP querier's robustness variable defines the maximum number of attempts for transmitting IGMP
general queries, group-specific queries, or group-and-source-specific queries in case of packet loss due to
network problems. A greater value of the robustness variable makes the IGMP querier "more robust", but
results in longer multicast group timeout time.
On startup, the IGMPv1/v2/v3 querier sends "startup query count" IGMP general queries at the "startup
query interval".
The IGMPv1/v2/v3 querier periodically sends IGMP general queries at the "IGMP general 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.
After receiving an IGMP leave message, the IGMPv2 querier sends "last-member query count" IGMP
group-specific queries at the "IGMP last-member query interval". After receiving an IGMP report that tells
relation changes between multicast groups and multicast sources, the IGMPv3 querier sends "last-member
query count" IGMP group-and-source-specific queries at the "IGMP last-member query interval". The value
of the "last-member query count" equals the value of the robustness variable.
After receiving an IGMP query (general query, group-specific query, or group-and-source-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 and IGMP group-and-source-specific queries, you can configure the
•
IGMP last-member query interval to fill their Max Response time field. Namely, for IGMP
group-specific queries and IGMP group-and-source-specific queries, the maximum response time
equals to 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".
Use the command...
igmp require-router-alert
igmp send-router-alert
75
Remarks
Optional.
By default, the router does not
check the Router-Alert option.
Optional.
By default, IGMP messages carry
the Router-Alert option.