H3C Technologies H3C SecPath F1000-E - Manual (Page 613)

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Step Command Remarks
2. Enter public network IGMP view. igmp N/A
3. Configure the router to discard
any IGMP message that does not
carry the Router-Alert option. require-router-alert
By default, the device
does not check the
Router-Alert option.
4. Enable insertion of the Router-Alert
option into IGMP messages.
send-router-alert
By default, IGMP
messages carry the
Router-Alert option.
To configure IGMP packet options on an interface:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Configure the interface to discard
any IGMP message that does not
carry the Router-Alert option.
igmp require-router-alert
By default, the device
does not check the
Router-Alert option.
4. Enable insertion of the Router-Alert
option into IGMP messages.
igmp send-router-alert
By default, IGMP
messages carry the
Router-Alert option.
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.