Cisco Systems 3560 Manual De Usuario

The Cisco IOS software supports these protocols to implement IP multicast routing: 

Internet Group Management Protocol (IGMP) is used among hosts on a LAN and the routers (and 
multilayer switches) on that LAN to track the multicast groups of which hosts are members.

Protocol-Independent Multicast (PIM) protocol is used among routers and multilayer switches to 
track which multicast packets to forward to each other and to their directly connected LANs. 

Distance Vector Multicast Routing Protocol (DVMRP) is used on the multicast backbone of the 
Internet (MBONE). The software supports PIM-to-DVMRP interaction.

Cisco Group Management Protocol (CGMP) is used on Cisco routers and multilayer switches 
connected to Layer 2 Catalyst switches to perform tasks similar to those performed by IGMP. 

 shows where these protocols operate within the IP multicast environment.

According to IPv4 multicast standards, the MAC destination multicast address begins with 0100:5e and 
is appended by the last 23 bits of the IP address. On the Catalyst 3560 switch, if the multicast packet 
does not match the switch multicast address, the packets are treated in this way:

If the packet has a multicast IP address and a unicast MAC address, the packet is forwarded in 
software. This can occur because some protocols on legacy devices use unicast MAC addresses with 
multicast IP addresses. 

If the packet has a multicast IP address and an unmatched multicast MAC address, the packet is 
dropped.

This section includes information about these topics:

PIM

IGMP

CGMP

DVMRP

Internet 
MBONE

Cisco Catalyst switch

(CGMP client)

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