What Is IGMP Snooping and IGMP Snooping Switch?

IGMP snooping switches are gradually entering the core of the network. Maybe some people are still not familiar with the fresh terms such as IGMP snooping, IGMP snooping switch, etc. What is IGMP snooping? What is IGMP snooping switch? All tells in this post.

What Is IGMP Snooping?

IGMP snooping, short for Internet Group Management Protocol Snooping, is a multicast constraint mechanism that runs on layer 2 devices to manage and control multicast groups. As shown in the following figure, this Layer 2 device is usually a data switch. The Layer 2 device (switch) running IGMP snooping analyzes the received IGMP messages and establishes a mapping relationship between the Layer 3 (router) and receivers. Then the layer 2 device (switch) forwards the multicast data according to the mapping relationship. When the layer 2 device (switch) is not running IGMP snooping, the multicast data is broadcast on the second layer. After the layer 2 device (switch) runs IGMP snooping, the multicast data of the multicast group is not broadcast on the second layer but among the known receivers on the second layer.

IGMP Snooping

Enable IGMP Snooping: Before and After

Types of IGMP Snooping

There are two types of IGMP snooping. One is passive and the other is active. The passive mode only parses multicast packets and does not filter packets. The active mode filters out multicast packets that are meaningless to the router. For example, two receivers under the switch using the passive mode are added to the same group, so that there is an entry in the router above the switch. If a receiver wants to leave the group, it sends a leave message to the router. However, even if the router receives the leave message, it does not delete the entry because there is another receiver in the multicast group. Different from the passive mode, the active mode enables the switch to filter out such packets.

What Is IGMP Snooping Switch?

A data switch with IGMP snooping is called an IGMP snooping switch. This kind switch can parse the IGMP packets passing through it and establish a multicast forwarding mapping relationship. In this way, the switch can forward multicast data according to the multicast mapping relationship. If this function is disabled, the switch can only broadcast multicast data. The practical application of IGMP snooping switch is to reduce the processing load caused by receivers on the network receiving unnecessary multicast packets. Most IGMP snooping switches use the active mode, so they can snoop the IGMP messages and leave messages and forward them only when necessary to the connected IGMP routers.


Today, IGMP snooping has become very common and advanced, and the current network supports multicast transmission. Besides, for the convenience and saving the load of the server, using the IGMP snooping switch is required. Although there are some shortcomings, the future of the this kind switch is promised. FS.COM can provide IGMP snooping 10Gbe switch. In addition to this, we also offer the Gigabit Ethernet switch for various ports. If you have any questions or needs about these, please visit www.fs.com.

What Is an Optical Cable and Why Do We Need It?

Fiber optic communication technology has emerged for a long time. It makes data transmission faster and faster, and itself has gradually become indispensable. Our business and daily life have benefited a lot from this technology. But how much do you know about fiber optic technology? What is an optical cable? What is an optical cable used for and why use optical cable? All tells in this post.

What Is an Optical Cable?

Optical cable, also known as fiber optic cable, is a kind of cable that has strands of glass or plastic fibers inside individual protective covers. The optical cable is used for digital data signals transferring in the form of light. The fiber optic cable distance can be up to hundreds of miles. In addition, optical cable has higher throughput rates than those achievable via electrical communication cables. As for fiber optic cable types, there are two common types: single mode fiber and multimode fiber.

No matter single mode fiber or multimode fiber, the basic fiber optic cable structure contains three parts: the core, cladding, and outer jacket. The cylindrical transparent core is very thin and flexible. The cladding is transparent, too. While the material of the cladding is different from that of the core. Finally, the outer jacket (or coating), whose main function is purely to protect the core and the cladding, is often made up of a strong and flexible material.

what is an optical cable structure

Figure: Fiber Optic Cable Structure

Why Use Optical Cable?

Getting to know what is an optical cable and what is an optical cable used for in the previous text, here comes to another point – why use optical cable. The fiber optic cable advantages are listed below.

  • Long Distance – As stated above, fiber optic cable distance can be up to hundred of miles. Generally, single mode fiber distance is about 200 km while multimode fiber distance is 2 km.
  • Fast Speed – Fiber optic cable speed varies on single mode fiber and multimode fiber. Single mode fiber speed is among 100 Mbit/s, 1 Gbit/s, 10 Gbit/s, 40 Gbit/s and 100 Gbit/s, but it usually runs at 40 Gbps or 100 Gbps for the long-haul data transmission. Multimode fiber speed is typically among 100 Mbit/s, 1 Gbit/s and 10 Gbit/s, but it also can support 40 Gbps or 100 Gbps for the relative short distance.
  • Overall Low Cost – With fiber network being common, optical cable price is not as high as before. You can choose single mode fiber patch cables and multimode fiber patch cables among various fiber optic cable manufacturers. FS.COM is a nice place to buy optical cables whose optical cable price is very low compared with other cable suppliers. And most of the fiber cables are in stock and ready for shipping.


After reading this post, you should be able to get a general picture of what is an optical cable and why do we need it. There is no doubt that the future of optical communication is expected, and optical communication will bring us more opportunities and convenience. If you have not deployed optical cable network, now is the time to begin. Please remember: buying optical cables from reliable fiber optic cable manufacturer would save you lots of money and maintenance time.