Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 165)

Multi-Service IronWare Multicast Configuration Guide 153
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IPv6 PIM Sparse
2
RP paths and SPT paths
Figure 19 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 19 , 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 scope-based
forwarding
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 Link-Local and are not forwarded. Thus, the implementation forwards only those
packets with an IPv6 multicast destination address with scope 4 or higher.
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 an IPv6 address on the interface.
• Enable IPv6 PIM Sparse.
• Identify the interface as an IPv6 PIM Sparse border, if applicable.
• Enable IPv6 Protocol Independent Multicast Sparse mode (PIM-SM) for a specified VRF, 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).
NOTE
It is recommended that you configure the same device as both the BSR and the RP.