最後更新: 2019-12-02


IGMP (Internet Group Management Protocol), 它是用來控制 multicast 的進行


  • IGMP V1
  • IGMP V2
  • IGMP V3

IGMP V1(RFC1112定義)


Router: Membership Query (每 60 秒 Query

PC: Membership Report

* IGMP Version 1沒有Leave訊息


IGMP V2(RFC2236定義)


 * 增加了 Leave Group Message

 * 增加了特定群組的查詢


IGMP V3(RFC 3376定義)



IGMP Proxy

actively filters IGMP packets in order to reduce load on the multicast router

The switch is trying to ensure the router only has a single report for the group,
regardless of how many active listeners there are.

IGMP snooping

A layer 2 optimization for the layer 3 IGMP.

IGMP snooping takes place internally on switches and is not a protocol feature.

A switch will, by default, flood multicast traffic to all the ports in a broadcast domain

IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined.

a mechanism to prune multicast traffic from links that do not contain a multicast listener (an IGMP client)