User’s Manual of FGSW-2620VM / FGSW-2620PVM

The states a computer will go through to join or to leave a multicast group are shown below:

Non-Member

Leave Group

 

Leave Group

(Stop Timer)

Join Group

 

 

 

(Send Report,

 

 

 

Start Timer)

 

 

 

 

 

 

Query Received

 

Delaying Member

(Start Timer)

Idle Member

Report Received

 

 

 

(Stop Timer)

 

 

Timer Expried

 

 

(Send report)

 

Figure 4-8-4:IGMP State Transitions

„IGMP Querier –

A router, or multicast-enabled switch, can periodically ask their hosts if they want to receive multicast traffic. If there is more than one router/switch on the LAN performing IP multicasting, one of these devices is elected “querier” and assumes the role of querying the LAN for group members. It then propagates the service requests on to any upstream multicast switch/router to ensure that it will continue to receive the multicast service.

Multicast routers use this information, along with a multicast routing protocol such as

DVMRP or PIM, to support IP multicasting across the Internet.

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