Implementing IPv6 Multicast
Information About Implementing IPv6 Multicast
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A route might have several paths to a destination prefix, such as when a router is configured for
simultaneous load balancing and redundancy. For each resolved path, a pointer is added for the
adjacency corresponding to the next-hop interface for that path. This mechanism is used for load
balancing across several paths.
Multiprotocol BGP for the IPv6 Multicast Address Family
The multicast BGP for the IPv6 multicast address family feature provides multicast BGP extensions for
IPv6 and supports the same features and functionality as IPv4 BGP. IPv6 enhancements to multicast
BGP include support for an IPv6 multicast address family and network layer reachability information
(NLRI) and next hop (the next router in the path to the destination) attributes that use IPv6 addresses.
Multicast BGP is an enhanced BGP that allows the deployment of interdomain IPv6 multicast. Multicast
BGP carries routing information for multiple network layer protocol address families; for example, IPv6
address family and for IPv6 multicast routes. The IPv6 multicast address family contains routes used for
RPF lookup by the IPv6 PIM protocol, and multicast BGP IPv6 provides for interdomain transport of
the same. Users must use multicast BGP for IPv6 multicast when using IPv6 multicast with BGP because
the unicast multicast BGP learned routes will not be used for IPv6 multicast.
Multicast BGP functionality provided through a separate address family context. A subsequent address
family identifier (SAFI) provides information about the type of the network layer reachability
information that is carried in the attribute. Multiprotocol BGP unicast uses SAFI 1 messages, and
multiprotocol BGP multicast uses SAFI 2 messages.
A separate BGP routing table is maintained to configure incongruent policies and topologies (for
example, IPv6 unicast and multicast) by using IPv6 multicast RPF lookup. Multicast RPF lookup is very
similar to the IP unicast route lookup.
No MRIB is associated with the IPv6 multicast BGP table. However, IPv6 multicast BGP operates on
the unicast IPv6 RIB when needed. Multicast BGP does not insert or update routes into the IPv6 unicast
RIB.
NSF and SSO Support In IPv6 Multicast
Support for nonstop forwarding (NSF) and stateful switchover (SSO) is provided in IPv6 Multicast. For
more information about NSF and SSO, see “Stateful Switchover” and “Cisco Nonstop Forwarding”in
the Cisco IOS High Availability Configuration Guide.
Bandwidth-Based CAC for IPv6 Multicast
The Bandwidth-Based Call Admission Control (CAC) for IPv6 Multicast feature implements a way to
count per-interface mroute state limiters using cost multipliers. This feature can be used to provide
bandwidth-based CAC on a per-interface basis in network environments where the multicast flows
utilize different amounts of bandwidth.
This feature limits and accounts for IPv6 multicast state in detail. When this feature is configured,
interfaces can be limited to the number of times they may be used as incoming or outgoing interfaces in
the IPv6 multicast PIM topology.
With this feature, router administrators can configure global limit cost commands for state matching
access lists and specify which cost multiplier to use when accounting such state against the interface
limits. This feature provides the required flexibility to implement bandwidth-based local CAC policy by
tuning appropriate cost multipliers for different bandwidth requirements.