Ethernet Switch IGMP Snooping Configuration: Solving the Multicast Traffic Flooding Dilemma in Video Surveillance
In the monitoring center of a smart park, operations and maintenance personnel found that the multicast traffic generated by 200 high-definition cameras within the park caused continuous congestion at the core switch ports, resulting in frequent video stuttering and even black screens. Upon investigation, it was discovered that traditional Layer 2 switches, unable to recognize multicast MAC addresses, broadcast all multicast traffic to every port, creating a typical "multicast flooding" phenomenon. This scenario reveals a common technical pain point in industrial video surveillance networks: how to achieve efficient forwarding of multicast data through precise traffic control?

1. The Fatal Impact of Multicast Flooding

1.1 Wasteful Consumption of Bandwidth Resources

Taking 4K cameras (with a bit rate of 8Mbps) as an example, when 200 cameras transmit simultaneously, the theoretical bandwidth requirement reaches 1.6Gbps. If the broadcast method is used, each switch port has to carry all the traffic, and the actual network load will grow exponentially. According to the measured data from a subway monitoring system, when IGMP Snooping is not enabled, multicast traffic occupies more than 90% of the bandwidth of the core switch, causing the transmission delay of critical business data to exceed 500ms.

1.2 Hidden Security Vulnerabilities in the Network

Multicast flooding provides attackers with a natural DDoS amplifier. In an attack incident experienced by an energy enterprise in 2025, the attacker made the switch forward malicious multicast traffic across the entire network by forging IGMP Join messages, resulting in the paralysis of the entire industrial control system for as long as 6 hours. Traditional firewalls lack effective defense measures against such attacks.

1.3 Excessive Wear and Tear on Device Performance

Continuous high-load operation causes the CPU utilization of the switch to soar above 95%. As a result, the monitoring network of a chemical enterprise experiences frequent switch restarts. Hardware acceleration modules are virtually useless in flooding scenarios. According to the actual measurement of a certain brand of switch, the multicast traffic processing efficiency is 70% lower than that of unicast traffic.

2. Decoding the IGMP Snooping Technology

2.1 Dynamic Forwarding Table Construction Mechanism

Ethernet switch automatically establishes a "multicast group-port" mapping table by listening to IGMP messages between the host and the router. Taking the USR-ISG series switches as an example, their ASIC chips can achieve:
Millisecond-level message parsing capability (<1ms)
8K MAC address table capacity
12Mbit data buffer space
When a camera sends an IGMP Join message, the switch immediately adds the corresponding port to the multicast forwarding table, and subsequent traffic is only forwarded to the target port. According to the actual measurement data, this mechanism can improve multicast forwarding efficiency by more than 90%.

2.2 Three Core Protection Functions

(1) Querier Election Mechanism
In a multi-switch cascaded environment, the USR-ISG competes to elect a unique querier through IGMP Query messages, avoiding network oscillation caused by multiple devices sending query messages simultaneously. According to the actual measurement in an automobile factory, this mechanism reduces the multicast member management response time from 3 seconds to 200ms.
(2) Member Report Suppression
When multiple hosts join the same multicast group, the switch automatically suppresses duplicate IGMP Report messages. In a test scenario with 200 cameras, this function reduces the uplink bandwidth occupation by 85%, significantly reducing the burden on core devices.
(3) Fast Leave Processing
For the common camera restart scenarios in video surveillance, the USR-ISG supports the IGMPv3 fast leave mechanism, which can immediately delete the port mapping after receiving a Leave message, avoiding continuous bandwidth occupation by residual traffic. According to the actual measurement in a smart agriculture project, this function reduces the network convergence time from 10 seconds to 500ms.

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3. Practical Guide to USR-ISG Configuration

3.1 Basic Function Deployment

Taking the renovation of a substation monitoring network as an example, the configuration steps are as follows:

After configuration, the switch automatically establishes a multicast forwarding table. According to the actual measurement, the bandwidth occupation is reduced from 1.2Gbps to 200Mbps.

3.2 Advanced Security Policies

For the forged query attacks faced by a smart park, an ACL filtering policy can be configured:

This configuration achieves a 100% interception rate of illegal query messages, effectively defending against man-in-the-middle attacks.

3.3 Industrial Environment Optimization

In the deployment in a high-temperature workshop (85°C environment) of a steel plant, the industrial-grade design of the USR-ISG demonstrates its advantages:

• Wide temperature operation: stable operation from -40°C to 85°C
• Vibration resistance: DIN rail mounting to withstand continuous vibration
• Lightning protection design: passes the IEC61000-4-5 standard and can withstand 4KV lightning strikes
  According to the actual measurement, it operates continuously for 365 days without failure, with an MTBF of 300,000 hours.

4. Analysis of Typical Application Scenarios

4.1 Smart Traffic Monitoring

A subway line uses the USR-ISG to build an on-board video surveillance system and achieves zero-interruption transmission through the following configuration:

This configuration keeps the packet loss rate below 0.001% when 1000 cameras transmit simultaneously.

4.2 Energy and Power Monitoring

A wind farm achieves precise forwarding of wind turbine monitoring data through the USR-ISG:

This configuration successfully intercepts 95% of illegal multicast traffic, significantly improving the network security level.

5. Selection Suggestions and Deployment Considerations

5.1 Comparison of Key Parameters

5.2 Deployment Topology Suggestions

For large-scale monitoring networks, it is recommended to adopt a three-layer architecture of "core-aggregation-access":

• Core Layer: Deploy high-end models of the USR-ISG and enable IGMPv3 and PIM-SM protocols
• Aggregation Layer: Configure static multicast routing to achieve traffic load balancing
• Access Layer: Enable the IGMP Snooping fast leave function to adapt to scenarios where terminals frequently start and stop
  After a smart park adopts this architecture, the network utilization rate is reduced from 70% to 40%, and the operation and maintenance costs are reduced by 60%.

6. Future Technological Evolution

With the penetration of SDN technology in the industrial field, the USR-ISG series has launched intelligent switch models that support OpenFlow, enabling:

• Centralized multicast flow table distribution
• Dynamic QoS policy adjustment
• Cross-domain multicast path optimization
  According to the actual measurement in an automobile factory, the SDN transformation shortens the new business deployment cycle from 2 weeks to 2 days and improves the multicast traffic forwarding efficiency by 40%.

As industrial video surveillance evolves towards high-definition and intelligentization, IGMP Snooping technology has become a core weapon for solving the multicast flooding problem. The USR-ISG series Ethernet switches are helping more than 2000 enterprises build efficient and secure monitoring networks with their industrial-grade reliability, refined traffic control, and scenario-based adaptability. Click the button and submit the form to obtain customized solutions tailored to your specific scenarios, making multicast traffic truly a driving force rather than an obstacle for industrial digital transformation.