Information About Basic IP Multicast Routing
IP multicasting is an efficient way to use network resources, especially for bandwidth-intensive services such as audio and video. IP multicast routing enables a host (source) to send packets to a group of hosts (receivers) anywhere within the IP network by using a special form of IP address called the IP multicast group address.
The sending host inserts the multicast group address into the IP destination address field of the packet, and IP multicast routers and multilayer devices forward incoming IP multicast packets out all interfaces that lead to members of the multicast group. Any host, regardless of whether it is a member of a group, can send to a group. However, only the members of a group receive the message.
Multicast Forwarding Information Base Overview
The device uses the Multicast Forwarding Information Base (MFIB) architecture and the Multicast Routing Information Base (MRIB) for IP multicast.
The MFIB architecture provides both modularity and separation between the multicast control plane (Protocol Independent Multicast [PIM] and Internet Group Management Protocol [IGMP]) and the multicast forwarding plane (MFIB). This architecture is used in Cisco IOS IPv6 multicast implementations.
MFIB itself is a multicast routing protocol independent forwarding engine; that is, it does not depend on PIM or any other multicast routing protocol. It is responsible for:
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Forwarding multicast packets
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Registering with the MRIB to learn the entry and interface flags set by the control plane
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Handling data-driven events that must be sent to the control plane
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Maintaining counts, rates, and bytes of received, dropped, and forwarded multicast packets
The MRIB is the communication channel between MRIB clients. Examples of MRIB clients are PIM, IGMP, the multicast routing (mroute) table, and the MFIB.
Default IP Multicast Routing Configuration
This table displays the default IP multicast routing configuration.
Feature |
Default Setting |
---|---|
Multicast routing |
Disabled on all interfaces. |
PIM version |
Version 2. |
PIM mode |
No mode is defined. |
PIM stub routing |
None configured. |
PIM RP address |
None configured. |
PIM domain border |
Disabled. |
PIM multicast boundary |
None. |
Candidate BSRs |
Disabled. |
Candidate RPs |
Disabled. |
Shortest-path tree threshold rate |
0 kb/s. |
PIM router query message interval |
30 seconds. |