CGMP router starts by sending a Join packet with the Group Destination MAC Address set to all zeros (meaning all multicast groups) and the source address as its own MAC address.

• 一个支持CGMP的路由器在发现网络上发送了一个带有分组目的MAC地址全为0（指所有的多目广播分组）的数据包后就会启动，源地址是它自己的地址。