What is the function of the interval for sending Query messages on an S series switch?

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For an S series switch, the interval for sending Query messages configured in a VLAN using the igmp-snooping query-interval command is used to:

- Control the interval at which Query messages are sent after the querier function is enabled in the VLAN.
- Calculate the aging time of dynamic member ports using the following formula:
Aging time = Robustness variable x Query interval + Maximum response time

Therefore, the interval is useful even when IGMP snooping querier is not enabled. In addition, you must configure the same interval on all devices when configuring IGMP snooping. Otherwise, some user-side interfaces may be incorrectly deleted, causing multicast forwarding interruption.

Other related questions:
Is the same interval for sending General Query messages required on S series switches
The interval for sending General Query messages is an important parameter used to calculate the aging time of multicast forwarding entries. When configuring this parameter on a multicast network, you are advised to configure the same value on all the devices. If multicast devices use different intervals, valid multicast forwarding entries may be aged out incorrectly, causing multicast traffic interruption. Devices from different vendors use different default intervals. When a network has devices from different vendors, configure the same interval on these devices. The default interval on S series switches is as follows: - IGMP: 60s on S series switches and E600 fixed switches - IGMP snooping: 60s on S series modular switches and 125s on S series and E600 fixed switches - MLD: 125s on S series switches and E600 fixed switches - MLD snooping: 60s on S series modular switches and 125s on S series and E600 fixed switches

Does an S series switch sends a Report message after receiving a Query message
If only IGMP snooping is enabled, an S series switch does not send Report messages after receiving Query messages. If IGMP snooping proxy or IGMP snooping Report suppression is also configured, the switch can construct and send Report messages according to existing entries after receiving Query messages.

In which situation can an S series switch send the option field in Request messages to a client
For S series switches excluding the S1700, the DHCP server returns the corresponding option field to a client only when the corresponding option field is encapsulated in the Request message.

How does an S series switch enabled with Layer 2 multicast send Query messages when the network topology changes
For an S series switch, when the ring network topology changes, Layer 2 multicast responds to two events by sending two Query messages with different source addresses. - Responds to the link change event of the ring network. Run the igmp-snooping send-query enable command to enable the switch to send IGMP Query messages in response to link change events. When receiving a link change event, the Layer 2 multicast module sends a Query message with source address 192.168.0.1 to all non-router ports. The source address can be changed using the igmp-snooping send-query source-address command. - Responds to the event that the interface changes from the Blocked state to the Forwarding state. Layer 2 multicast sends a Query message whose source address is 0. The message is sent to only the interface of which the status changes. According to RFCs, Query messages whose source address is 0 cannot be used for querier election. Therefore, the Query message sent when the interface status changes will not affect querier election, but the Query message sent when the link changes may affect querier election. You can configure a static router interface to prevent Query messages from affecting querier election.

Functions of the GIADDR field of DHCP messages on S series switches
Functions of the GIADDR field of DHCP messages on S series switches: he GIADDR field (gateway IP address) in DHCP messages records the IP address of the first DHCP relay agent that DHCP messages pass through. After a client sends a DHCP Request message, the first DHCP relay agent fills its own IP address in this field when forwarding this DHCP Request message to the DHCP server if the server and the client are located on different network segments. The DHCP server uses the field to determine the network segment on which a client resides so that the server can assign an IP address on this network segment to the client.

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