C H A P T E R 40 Configuring Ip Multicast Routing; Understanding Cisco's Implementation Of Ip Multicast Routing - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Understanding Cisco's Implementation of IP Multicast Routing

Understanding Cisco's Implementation of IP Multicast Routing
The Cisco IOS software supports these protocols to implement IP multicast routing:
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Figure 40-1
Figure 40-1
Host
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 3750 switch, if the multicast packet
does not match the switch multicast address, the packets are treated in this way:
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This section includes information about these topics:
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Catalyst 3750 Switch Software Configuration Guide
40-2
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.
IP Multicast Routing Protocols
Cisco Catalyst switch
CGMP
Host
IGMP
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.
Understanding IGMP, page 40-3
Understanding PIM, page 40-4
Understanding DVMRP, page 40-7
Understanding CGMP, page 40-8
(CGMP client)
PIM
Chapter 40 Configuring IP Multicast Routing
Internet
MBONE
DVMRP
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