/ / IGMP snooping: concept and use

IGMP snooping: concept and use

To group network devices into groupsIP nodes and routers use the IGMP management protocol. Internet Group Management Protocol manages multicast (group) data transmission in 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 the other clients via the PIM protocol. It connects the local router to the remote router. Thanks to the application of IGMP, the network resources of a number of applications (online games, streaming video) can be used more efficiently.

Make the decision to broadcast traffic to those orOther interfaces allow the use of the IGMP snooping function. What it is? This is the process of tracking IGMP requests from consumers (hosts) to providers (group routers).

igmp snooping

Concept and purpose of IGMP snooping

In English, snooping means"eavesdropping". When enabled, the intermediate network device (router or communicator) begins to analyze the transfer of all data packets between client computers connected to it and routers that supply group traffic. When a connection request is detected, the port to which the consumer is connected (the client) is turned on, in the opposite situation (Leave request), the corresponding port is removed from the group list.

In most communicators, IGMP snooping is available, but requires pre-activation.

Why monitor network traffic?

Multicast-traffic can be transmitted includingto computers that are not interested in it. This is called broadcast retransmission. To prevent this, IGMP snooping is used to reduce the load on the network. At the same time, this kind of filtering requires additional memory and increases the load on the communicator. However, it is justified.

If the communicator starts broadcasting group traffic on all its ports, then:

  • this process is useless;
  • there may be problems in the work of the ultimate recipient (network device), forced to handle a large flow of unnecessary data.

To avoid such situations, there isIGMP snooping, which significantly improves the performance of the entire network. It takes into account the needs at the network (third) level and thus optimizes the channel (second) level of data transmission.

enable igmp snooping

Enabling the wiretap feature

In order to track multicast-traffic,you must first enable IGMP snooping and configure it yourself. Consider how to do this on D-Link communicators when implementing a multicast data scheme. Commands for activating the network listening:

igmp commands

In order to exclude a port from a network group,When the communicator receives 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 in order to more efficiently work. To activate this function, use the following command:

igmp leave

Applicable if you want to enable multicast filtering of the switch with a node connected to it that is involved in the data transfer.

Types of IGMP-wiretapping

The IGMP snooping function can be either passive or active. How is it shown?

  1. Passive does not filter traffic, but simply tracks it.
  2. Active - listen and filter data packets to reduce the load on the group router.

The second type of implementation of this function ismost preferable, because it allows you to minimize the amount of information transferred by filtering requests for connection to the router and disconnecting from it.

igmp snooping what is this

Functionality of IGMP snooping-communicatorhelps to reduce the load on the network by monitoring the processes of data exchange between providers (local routers) and consumers (client computers) of group traffic.