configuration needs to be applied on all the routers in the multicast network. To automate this process, the
Auto-RP protocol was devised.
This Cisco proprietary feature eliminates the need to manually configure the RP information in every router
and multilayer switch in the network. For Auto-RP to work, you configure a Cisco router or multilayer switch
as the mapping agent. It uses IP multicast to learn which routers or switches 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 switch 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 switches automatically discover which RP to use for the groups that they support. If a router or switch
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 switch 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, on page 50
Adding Auto-RP to an Existing Sparse-Mode Cloud, on page 52
Example: Configuring Auto-RP, on page 72
Example: Defining the IP Multicast Boundary to Deny Auto-RP Information, on page 72
Example: Filtering Incoming RP Announcement Messages, on page 72
Auto-RP Benefits
Auto-RP uses IP multicast to automate the distribution of group-to-RP mappings to all Cisco routers and
multilayer switches in a PIM network. Auto-RP has these benefits:
•
Easy to use multiple RPs within a network to serve different group ranges.
•
Provides load splitting among different RPs and arrangement of RPs according to the location of group
participants.
•
Avoids inconsistent, manual RP configurations on every router and multilayer switch in a PIM network,
which can cause connectivity problems.
Follow these guidelines when configuring Auto-RP:
•
If you configure PIM in sparse mode or sparse-dense mode and do not configure Auto-RP, you must
manually configure an RP.
•
If routed interfaces are configured in sparse mode, Auto-RP can still be used if all devices are configured
with a manual RP address for the Auto-RP groups.
•
If routed interfaces are configured in sparse mode and you enter the ip pim autorp listener global
configuration command, Auto-RP can still be used even if all devices are not configured with a manual
RP address for the Auto-RP groups.
Catalyst 2960-XR Switch IP Multicast Routing Configuration Guide, Cisco IOS Release 15.0(2)EX1
OL-29426-01 41
Configuring PIM
Auto-RP
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