The Role Of Auto-Rp In A Pim Network; Ip Multicast Routing Configuration Guide, Cisco Ios Xe Release 3Se (Catalyst 3650 Switches - Cisco Catalyst 3650 Configuration Manual

Auto-RP
This Cisco proprietary feature eliminates the need to manually configure the RP information in every router
and multilayer device in the network. For Auto-RP to work, you configure a Cisco router or multilayer device
as the mapping agent. It uses IP multicast to learn which routers or devices in the network are possible candidate
RPs to receive candidate RP announcements. Candidate RPs periodically send multicast RP-announce messages
to a particular group or group range to announce their availability.
Mapping agents listen to these candidate RP announcements and use the information to create entries in their
group-to-RP mapping caches. Only one mapping cache entry is created for any group-to-RP range received,
even if multiple candidate RPs are sending RP announcements for the same range. As the RP-announce
messages arrive, the mapping agent selects the router or device with the highest IP address as the active RP
and stores this RP address in the group-to-RP mapping cache.
Mapping agents periodically multicast the contents of their group-to-RP mapping caches. Thus, all routers
and devices automatically discover which RP to use for the groups that they support. If a router or device fails
to receive RP-discovery messages and the group-to-RP mapping information expires, it changes to a statically
configured RP that was defined with the ip pim rp-address global configuration command. If no statically
configured RP exists, the router or device changes the group to dense-mode operation.
Multiple RPs serve different group ranges or serve as hot backups of each other.
Related Topics
Setting Up Auto-RP in a New Internetwork (CLI), on page 129
Example: Configuring Auto-RP, on page 157

The Role of Auto-RP in a PIM Network

Auto-RP automates the distribution of group-to-rendezvous point (RP) mappings in a PIM network. To make
Auto-RP work, a device must be designated as an RP mapping agent, which receives the RP announcement
messages from the RPs and arbitrates conflicts. The RP mapping agent then sends the consistent group-to-RP
mappings to all other devices by way of dense mode flooding.
Thus, all routers automatically discover which RP to use for the groups they support. The Internet Assigned
Numbers Authority (IANA) has assigned two group addresses, 224.0.1.39 and 224.0.1.40, for Auto-RP.
The mapping agent receives announcements of intention to become the RP from Candidate-RPs. The mapping
agent then announces the winner of the RP election. This announcement is made independently of the decisions
by the other mapping agents.
Related Topics
Configuring Sparse Mode with Auto-RP, on page 146
Example: Sparse Mode with Auto-RP , on page 158

IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)

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Configuring PIM
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