max-response-time (IGMP)

Function

The max-response-time command sets a global maximum response time for IGMP General Query messages.

The undo max-response-time command restores the global maximum response time for IGMP General Query messages to the default value.

By default, the global maximum response time for IGMP General Query messages is 10 seconds.

Format

max-response-time interval

undo max-response-time

Parameters

Parameter	Description	Value
interval	Specifies the maximum response time for IGMP General Query messages.	The value is an integer that ranges from 1 to 25, in seconds.

Views

IGMP view of the public network instance, IGMP view of a VPN instance

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

If hosts send IGMP Report messages immediately after they receive IGMP General Query messages, the querier on a shared network segment may receive a large number of Report messages sent from many hosts at the same time. This may cause congestion on the network.

To avoid such situations, IGMPv2 and IGMPv3 messages specify the maximum response time for IGMP General Query messages. When a host running IGMPv2 or IGMPv3 receives an IGMP General Query message, it starts a timer for the group it wants to join. The timer length is a random value between 0 and the maximum response time. When the timer times out, the host sends a Report message.

The maximum response time specifies the deadline for the host to send a Report message. An appropriate maximum response time allows hosts to respond to Query messages quickly and prevents hosts from sending Report messages at the same time.

Prerequisites

IP multicast routing has been enabled using the multicast routing-enable command.

Precautions

This command applies only to IGMPv2 and IGMPv3.
A smaller response time allows the switch to learn multicast memberships more quickly but occupies more bandwidth and system resources.
This command has the same function as the igmp max-response-time command used in the interface view. The configuration in the IGMP view is globally valid, whereas the configuration in the interface view takes effect only for the specified interface. The configuration in the interface view takes precedence over the configuration in the IGMP view. The configuration in the IGMP view is used only when no configuration is performed in the interface view.

Example

# In the IGMP view, set the maximum response time for IGMP General Query messages to 8 seconds.

<HUAWEI> system-view
[HUAWEI] multicast routing-enable
[HUAWEI] igmp
[HUAWEI-igmp] max-response-time 8