Anycast-Rp; Pim Register Messages - Cisco Nexus 7000 Series Configuration Manual

Configuring PIM and PIM6

Anycast-RP

Anycast-RP has two implementations: one uses Multicast Source Discovery Protocol (MSDP) and the other
is based onRFC 4610, Anycast-RP Using Protocol Independent Multicast (PIM). This section describes how
to configure PIM Anycast-RP.
You can use PIM Anycast-RP to assign a group of routers, called the Anycast-RP set, to a single RP address
that is configured on multiple routers. The set of routers that you configure as Anycast-RPs is called the
Anycast-RP set. This method is the only RP method that supports more than one RP per multicast group,
which allows you to load balance across all RPs in the set. The Anycast RP supports all multicast groups.
PIM register messages are sent to the closest RP and PIM join-prune messages are sent in the direction of the
closest RP as determined by the unicast routing protocols. If one of the RPs goes down, unicast routing ensures
these message will be sent in the direction of the next-closest RP.
You must configue PIM on the loopback interface that is used for the PIM Anycast RP.
For more information about PIM Anycast-RP, see RFC 4610.
For information about configuring Anycast-RPs, see Configuring a PIM Anycast-RP Set.

PIM Register Messages

PIM register messages are unicast to the RP by designated routers (DRs) that are directly connected to multicast
sources. The PIM register message has the following functions:
• To notify the RP that a source is actively sending to a multicast group.
• To deliver multicast packets sent by the source to the RP for delivery down the shared tree.
The DR continues to send PIM register messages to the RP until it receives a Register-Stop message from the
RP. The RP sends a Register-Stop message in either of the following cases:
• The RP has no receivers for the multicast group being transmitted.
• The RP has joined the SPT to the source but has not started receiving traffic from the source.
You can use the ip pim register-source command to configure the IP source address of register messages
when the IP source address of a register message is not a uniquely routed address to which the RP can send
packets. This situation might occur if the source address is filtered so that the packets sent to it are not forwarded
or if the source address is not unique to the network. In these cases, the replies sent from the RP to the source
address will fail to reach the DR, resulting in Protocol Independent Multicast sparse mode (PIM-SM) protocol
failures.
This example shows how to configure the IP source address of the register message to the loopback 3 interface
of a DR:
ip pim register-source loopback 3
Note In Cisco NX-OS, PIM register messages are rate limited to avoid overwhelming the RP.
You can filter PIM register messages by defining a routing policy. For information about configuring the PIM
register message policy, see the Configuring Shared Trees Only for ASM.
Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide
Anycast-RP
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