Cisco Catalyst 3560-X Software Configuration Manual page 1327
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Also See for Catalyst 3560-X:
- Command reference manual (1188 pages) ,
- Software configuration manual (1438 pages) ,
- Manual (276 pages)
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Chapter 1
Implementing IPv6 Multicast
IPv6 BSR: Configure RP Mapping
PIM switches in a domain must be able to map each multicast group to the correct RP address. The BSR
protocol for PIM-SM provides a dynamic, adaptive mechanism to distribute group-to-RP mapping
information rapidly throughout a domain. With the IPv6 BSR feature, if an RP becomes unreachable, it
will be detected and the mapping tables will be modified so that the unreachable RP is no longer used,
and the new tables will be rapidly distributed throughout the domain.
Every PIM-SM multicast group needs to be associated with the IP or IPv6 address of an RP. When a new
multicast sender starts sending, its local DR will encapsulate these data packets in a PIM register
message and send them to the RP for that multicast group. When a new multicast receiver joins, its local
DR will send a PIM join message to the RP for that multicast group. When any PIM switch sends a (*,
G) join message, the PIM switch needs to know which is the next switch toward the RP so that G (Group)
can send a message to that switch. Also, when a PIM switch is forwarding data packets using (*, G) state,
the PIM switch needs to know which is the correct incoming interface for packets destined for G, because
it needs to reject any packets that arrive on other interfaces.
A small set of switches from a domain are configured as candidate bootstrap switches (C-BSRs) and a
single BSR is selected for that domain. A set of switches within a domain are also configured as
candidate RPs (C-RPs); typically, these switches are the same switches that are configured as C-BSRs.
Candidate RPs periodically unicast candidate-RP-advertisement (C-RP-Adv) messages to the BSR of
that domain, advertising their willingness to be an RP. A C-RP-Adv message includes the address of the
advertising C-RP, and an optional list of group addresses and mask length fields, indicating the group
prefixes for which the candidacy is advertised. The BSR then includes a set of these C-RPs, along with
their corresponding group prefixes, in bootstrap messages (BSMs) it periodically originates. BSMs are
distributed hop-by-hop throughout the domain.
Bidirectional BSR support allows bidirectional RPs to be advertised in C-RP messages and bidirectional
ranges in the BSM. All switches in a system must be able to use the bidirectional range in the BSM;
otherwise, the bidirectional RP feature will not function.
PIM-Source Specific Multicast
PIM-SSM is the routing protocol that supports the implementation of SSM and is derived from PIM-SM.
However, unlike PIM-SM where data from all multicast sources are sent when there is a PIM join, the
SSM feature forwards datagram traffic to receivers from only those multicast sources that the receivers
have explicitly joined, thus optimizing bandwidth utilization and denying unwanted Internet broadcast
traffic. Further, instead of the use of RP and shared trees, SSM uses information found on source
addresses for a multicast group. This information is provided by receivers through the source addresses
relayed to the last-hop switches by MLD membership reports, resulting in shortest-path trees directly to
the sources.
In SSM, delivery of datagrams is based on (S, G) channels. Traffic for one (S, G) channel consists of
datagrams with an IPv6 unicast source address S and the multicast group address G as the IPv6
destination address. Systems will receive this traffic by becoming members of the (S, G) channel.
Signaling is not required, but receivers must subscribe or unsubscribe to (S, G) channels to receive or
not receive traffic from specific sources.
MLD version 2 is required for SSM to operate. MLD allows the host to provide source information.
Before SSM can run with MLD, SSM must be supported in the Cisco IOS IPv6 switch, the host where
the application is running, and the application itself.
OL-25303-03
Information About Implementing IPv6 Multicast
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
1-7
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