RP paths and SPT paths
between the receiver and the source (the Shortest Path Tree, or SPT) and uses the SPT for subsequent packets from the source to the receiver. The device calculates a separate SPT for each
NOTE
It is recommended that you configure the same ports as candidate BSRs and RPs.
RP paths and SPT paths
Figure 10 on page 164 shows two paths for packets from the source for group fec0:1111::1 and a receiver for the group. The source is attached to PIM Sparse router A and the recipient is attached to PIM Sparse router C. PIM Sparse router B is the RP for this multicast group. As a result, the default path for packets from the source to the receiver is through the RP. However, the path through the RP sometimes is not the shortest path. In this case, the shortest path between the source and the receiver is over the direct link between router A and router C, which bypasses the RP (router B).
To optimize PIM traffic, the protocol contains a mechanism for calculating the Shortest Path Tree (SPT) between a given source and a receiver. PIM Sparse routers can use the SPT as an alternative to using the RP for forwarding traffic from a source to a receiver. By default, the device forwards the first packet it receives from a given source to a given receiver using the RP path, but subsequent packets from that source to that receiver through the SPT. In Figure 10 on page 164, router A forwards the first packet from group fec0:1111::1 source to the destination by sending the packet to router B, which is the RP. Router B then sends the packet to router C. For the second and all future packets that router A receives from the source for the receiver, router A forwards them directly to router C using the SPT path.
RFC 3513 and RFC 4007 compliance for IPv6 multicast
The IPv6 multicast implementation recognizes scopes and conforms to the scope definitions in RFC 3513. Per RFC 3513, scopes 0 and 3 are reserved and packets are not forwarded with an IPv6 destination multicast address of scopes 0 and 3. Additionally, scopes 1 and 2 are defined as Node- Local and
RFC 4007 defines ‘scope zones’ and requires that the forwarding of packets received on any interface of a particular scope zone be restricted to that scope zone. Currently, the device supports one zone for each scope, and the default zone for scope 4 and higher consists of all interfaces in the system. Thus, the default zones for scope 4 and higher are the same size.
Configuring PIM Sparse
To configure the device for IPv6 PIM Sparse, perform the following tasks:
•Enable the IPv6 PIM Sparse of multicast routing.
•Configure VRF then enable IPv6 Protocol Independent Multicast Sparse mode
•Configure an IPv6 address on the interface.
•Enable IPv6 PIM Sparse.
•Identify the interface as an IPv6 PIM Sparse border, if applicable.
•Identify the device as a candidate PIM Sparse Bootstrap Router (BSR), if applicable.
•Identify the device as a candidate PIM Sparse Rendezvous Point (RP), if applicable.
•Specify the IP address of the RP (if you want to statically select the RP).
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