IP nodes and routers use the IGMP management protocol to group network devices. The Internet Group Management Protocol manages multicast data transmission over networks. It is located at the network level and connects the client computer to the local router in order to transfer data between them. Then group traffic is routed to other clients through the PIM protocol. It associates a local router with a remote one. Thanks to IGMP, the network resources of a number of applications (online games, video streaming) can be used more efficiently.
Using the IGMP snooping function allows you to make a decision about broadcasting traffic to various interfaces. What it is? This is the process of tracking IGMP requests from consumers (hosts) to providers (group routers).
IGMP snooping concept and purpose
Translated from English snooping means "eavesdropping". When it is turned on, an intermediate network device (router or communicator) begins to analyze the transmission of all data packets between the client computers connected to it and the routers that supply group traffic. When a connection request is detected, the port to which the consumer (client) is connected is turned on, in the opposite situation (Leave request), the corresponding port is deleted from the group list.
On most communicators, the IGMP snooping feature is available but needs to be enabled first.
Why monitor network traffic?
Multicast traffic can also be transmitted to computers that are not interested in it. This is called broadcast relay. To prevent it, in order to reduce the load on the network, IGMP snooping is used. At the same time, this kind of filtering requires additional memory costs and increases the load on the communicator. However, she is justified.
If the communicator starts broadcasting group traffic on all its ports, then:
- this process is useless;
- problems may arise in the operation of the final recipient (network device), which is forced to process a large stream of unnecessary data.
To eliminate such situations, there is an IGMP snooping function that significantly improves the operation of the entire network. It takes into account the needs at the network (third) level and thus optimizes the channel (second) level of data transfer.
Turn on the wiretap function
In order to monitor multicast traffic, you must first enable IGMP snooping and configure it yourself. Let's see how to do this on D-Link communicators when implementing a multicast data transfer scheme. Commands for activating network wiretapping:
In order to exclude a port from the network group when the communicator received a Leave request from the client, the IGMP Snooping Fast Leave function is used. It allows you to stop the transmission of unnecessary data streams over the network with a view to its more efficient operation. To activate this function, use the following command:
It is used if it is necessary to enable multicast filtering of a switch with a node connected to it and participating in data transmission.
Types of IGMP wiretapping
The IGMP snooping function can be either passive or active. How is it shown?
- Passive does not filter traffic, but simply tracks it.
- Active - listening and filtering data packets are performed to reduce the load on the group router.
The second type of implementation of this function is most preferable, since it allows you to minimize the amount of information transmitted by filtering requests to connect to and disconnect from the router.
The functionality of the IGMP snooping communicator helps to reduce the load on the network by monitoring the data exchange processes between providers (local routers) and consumers (client computers) of group traffic.