Configuring IGMP Querier Parameters
Context
IGMP maintains group memberships using Query and Report messages. When multiple multicast routers exist on a network segment, an IGMP querier is elected among them to send IGMP Query messages. The IGMP querier can work normally using default settings of querier parameters. You can modify the querier parameters to enable the querier to update group membership in a timely manner and avoid network congestion.
Table 2-9 lists description and default setting of IGMP querier parameters.
Parameter |
Description |
Default Setting |
|---|---|---|
Interval for sending IGMP General Query messages |
The querier sends IGMP General Query messages at the specified interval to maintain memberships of interfaces. This parameter specifies the interval for sending IGMP General Query messages. |
60s |
Robustness variable of the IGMP querier |
The robustness variable of the IGMP querier specifies the retransmission count of IGMP packets to minimize impact of packet loss on the network. The robustness variable defines the following values:
|
2 |
Maximum response time for IGMP General Query messages |
After a multicast member receives an IGMP General Query message, it must send a Report message to the IGMP querier within the maximum response time. |
10s |
Other querier present interval |
If non-queriers do not receive any Query message within the Keepalive period, they consider the querier invalid and trigger election of a new querier. |
125s if the robustness variable, interval for sending IGMP General Query messages, and maximum response time are all default values |
Interval for sending IGMP Group-Specific Query messages or IGMP Group-and-Source-Specific Query messages |
When the querier receives a Done message that a host sends to leave a multicast group, the querier periodically sends Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages to check for other members in the multicast group. This parameter specifies the interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages. |
1s |
If IGMP is enabled on user-side interfaces of multiple devices on a shared network segment, the devices must have the same querier configuration. Otherwise, IGMP may not function normally.
The IGMP querier parameters can be configured in the IGMP view or interface view.
- The configuration in the IGMP view is valid globally, whereas the configuration in the interface view is valid only for the specific interface.
- If a querier parameter is configured in the interface view and the IGMP view, the configuration in the interface view takes precedence over the configuration in the IGMP view. If a querier parameter is not configured on an interface, the interface uses the configuration in the IGMP view.
- If non-default configuration is made in the IGMP view, the default configuration in the interface view does not take effect.
Procedure
- Configuring global IGMP querier parameters
Ensure that the interval for sending General Query messages is larger than the maximum response time for IGMP Query messages and is smaller than the other querier present interval; otherwise IGMP Report messages may not be sent in response to IGMP Query messages in a timely manner, causing the device to delete multicast entries.
- Configuring IGMP querier parameters on an interface
Ensure that the interval for sending General Query messages is larger than the maximum response time for IGMP Query messages and is smaller than the other querier present interval; otherwise IGMP Report messages may not be sent in response to IGMP Query messages in a timely manner, causing the device to delete multicast entries.