Advantages of IGMP Snooping

26

When there are multicast services, IGMP Snooping used on Layer 2 devices brings the following advantages:
Saves network bandwidth.
Improves information security because packet services are independently forwarded using VLANs.
Reduces interruption time of multicast services and enhances reliability because network topology changes can be sensed in a timely manner.

Other related questions:
Difference between IGMP snooping and IGMP snooping proxy on an S series switch
IGMP snooping and IGMP snooping proxy have the same functions but different mechanisms. IGMP snooping obtains required information by listening to IGMP messages; IGMP snooping proxy intercepts and suppresses IGMP requests of terminal users, and then forwards the requests to the router. The Layer 2 network device with IGMP Snooping Proxy configured functions as a server on the user side. It periodically queries user information. On the network side, this switch functions as a client and reports user information after receiving query messages. Therefore, IGMP snooping proxy can not only suppress multicast packets on Layer 2 network, but also reduce the total number of protocol packets on the network. The proxy router is required for maintaining and calculating entry status changes, so the implementation is more complex and the cost is added.

IGMP snooping configuration on S series switch
With IGMP snooping configured, the switch listens to and analyzes IGMP packets exchanged between multicast users and the upstream router, and creates Layer 2 multicast forwarding entries based on IGMP packet information. Multicast data packets are then forwarded based on the Layer 2 multicast forwarding entries, instead of being broadcast on the Layer 2 network. For example, to enable IGMP snooping in VLAN 10 on an S series switch, except S1700, run the following commands: [HUAWEI] igmp-snooping enable //Enable IGMP snooping globally. [HUAWEI] vlan 10 [HUAWEI-vlan10] igmp-snooping enable //Enable IGMP snooping in the VLAN.

Configure IGMP snooping on the AR router
With IGMP snooping configured, the Layer 2 multicast device listens to and analyzes IGMP packets exchanged between multicast users and the upstream router, and creates Layer 2 multicast forwarding entries accordingly. Multicast data packets are then forwarded based on the Layer 2 multicast forwarding entries. This prevents the multicast data from being broadcast on the Layer 2 network. On an AR router, enable IGMP snooping in VLAN 10. The configuration is as follows: [HUAWEI] igmp-snooping enable //Enable IGMP snooping globally. [HUAWEI] vlan 10 command. [HUAWEI-vlan10] igmp-snooping enable //Enable IGMP snooping in VLAN 10.

IGMP snooping parameters of an S series switch
The following IGMP snooping parameters are provided: - Query-interval: specifies the interval for sending General Query messages. The system starts an aging timer for a member port when the port receives a Report message. The aging time is calculated using the following formula: Aging time = Robust variable x Query interval + Maximum response time for General Query messages On the S series modular switch, the default value is 60s. On S and E series fixed switches excluding the S1700, the default value is 125s. - Max-response-time: specifies the maximum response time for a Query message. After receiving a Query message, a device must send a response message within the specified time. The device may send the Report message at any time before the maximum response time expires. The default interval is 10s. - Robust-count: specifies the IGMP robustness variable. This parameter is set based on the link performance. If a link is unstable and many packets are discarded, increase the robustness variable. The default robustness variable is 2. - Last-member-query-interval: specifies the interval for sending Last Member Query messages. In IGMPv2 and IGMPv3, the system starts an aging timer for a member port when the port receives a Leave message. The aging time is calculated using the following formula: Aging time = Robust variable x Interval for sending Last Member Query messages The default interval is 1s. If the IGMP snooping querier is not configured, the parameter is used to calculate the aging time of member ports. - After a member port receives a Report message from the downstream host, the aging time is as follows: Aging time = Robust variable x Query interval + Maximum response time for General Query messages - After a member port receives a Leave message from the downstream host, the aging time is as follows: Aging time = Robust variable x Interval for sending Last Member Query messages Run the display igmp-snooping command to check parameter settings on an S series switch excluding the S1700.

If you have more questions, you can seek help from following ways:
To iKnow To Live Chat
Scroll to top