Configuring a Rendezvous Point
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Table Of Contents
Configuring a Rendezvous Point
Recommended Methods for Configuring an RP
Auto-RP with Multiple RPs Scenario
BSR with Multiple RPs Scenario
Anycast RP with Auto-RP Scenario
Configuring a Rendezvous Point
Version History
The purpose of this document is to outline four recommended methods for configuring a rendezvous point (RP) in a Protocol Independent Multicast sparse mode (PIM-SM) network. It provides scenario descriptions and basic configuration examples for each option.
This document has the following sections:
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Recommended Methods for Configuring an RP
Rendezvous Point Overview
A rendezvous point (RP) is required only in networks running Protocol Independent Multicast sparse mode (PIM-SM). The protocol is described in RFC 2362. In PIM-SM, only network segments with active receivers that have explicitly requested multicast data will be forwarded the traffic. This method of delivering multicast data is in contrast to the PIM dense mode (PIM-DM) model. In PIM-DM, multicast traffic is initially flooded to all segments of the network. Routers that have no downstream neighbors or directly connected receivers prune back the unwanted traffic.
An RP acts as the meeting place for sources and receivers of multicast data. In a PIM-SM network, sources must send their traffic to the RP. This traffic is then forwarded to receivers down a shared distribution tree. By default, when the first hop router of the receiver learns about the source, it will send a join message directly to the source, creating a source-based distribution tree from the source to the receiver. This source tree does not include the RP unless the RP is located within the shortest path between the source and receiver.
In most cases, the placement of the RP in the network is not a complex decision. By default, the RP is needed only to start new sessions with sources and receivers. Consequently, the RP experiences little overhead from traffic flow or processing. In PIM-SM version 2, the RP requires less processing than in PIM-SM version 1 because sources must only periodically register with the RP to create state.
RP Configuration Overview
In the first version of PIM-SM, all leaf routers (routers directly connected to sources or receivers) were required to be manually configured with the IP address of the RP. This type of configuration is also known as static RP configuration. Configuring static RPs is relatively easy in a small network, but it can be laborious in a large, complex network.
Following the introduction of PIM-SM version 1, Cisco implemented a version of PIM-SM with the Auto-RP feature. Auto-RP automates the distribution of group-to-RP mappings in a PIM network. To make Auto-RP work, a router 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 routers by 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. One advantage of Auto-RP is that any change to the RP designation must be configured only on the routers that are RPs and not on the leaf routers. Another advantage of Auto-RP is that it offers the ability to scope the RP address within a domain. Scoping can be achieved by defining the time-to-live (TTL) value allowed for the Auto-RP advertisements.
Another RP selection model called bootstrap router (BSR) was introduced after Auto-RP in PIM-SM version 2. BSR performs similarly to Auto-RP in that it uses candidate routers for the RP function and for relaying the RP information for a group. RP information is distributed through BSR messages, which are carried within PIM messages. PIM messages are link-local multicast messages that travel from PIM router to PIM router. Because of this single hop method of disseminating RP information, TTL scoping cannot be used with BSR. A BSR performs similarly as an RP, except that it does not run the risk of reverting to dense mode operation, and it does not offer the ability to scope within a domain.
Each method for configuring an RP has its own strengths, weaknesses, and level of complexity. In conventional IP multicast network scenarios, we recommend using Auto-RP to configure RPs because it is easy to configure, well-tested, and stable.
Sparse-Dense Mode for Auto-RP
A prerequisite of Auto-RP is that all interfaces must be configured in sparse-dense mode using the ip pim sparse-dense-mode interface configuration command. An interface configured in sparse-dense mode is treated in either sparse mode or dense mode of operation, depending on which mode the multicast group operates. If a multicast group has a known RP, the interface is treated in sparse mode. If a group has no known RP, the interface is treated in dense mode and data will be flooded over this interface.
To successfully implement Auto-RP and prevent any groups other than 224.0.1.39 and 224.0.1.40 from operating in dense mode, we recommend configuring a "sink RP" (also known as "RP of last resort"). A sink RP is a statically configured RP that may or may not actually exist in the network. Configuring a sink RP does not interfere with Auto-RP operation because, by default, Auto-RP messages supersede static RP configurations. We recommend configuring a sink RP for all possible multicast groups in your network, because it is possible for an unknown or unexpected source to become active. If no RP is configured to limit source registration, the group may revert to dense mode operation and be flooded with data.
Auto-RP Filters
When using Auto-RP, configure the ip pim rp-announce-filter global configuration command on Auto-RP mapping agent routers to filter Auto-RP announcement messages that arrive on group 224.0.1.39 from candidate RP routers. This command prevents unwanted candidate RP announcement messages from being processed by the mapping agent. Unwanted messages could interfere with the RP election mechanism of the mapping agent.
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The following example shows how to configure the router to accept announcements from RP addresses 10.0.0.1 and 10.0.0.2. This router is also configured to accept announcements for all groups.
ip pim rp-announce-filter rp-list 1 group-list 2access-list 1 permit 10.0.0.1access-list 1 permit 10.0.0.2access-list 2 permit 224.0.0.0 15.255.255.255Recommended Methods for Configuring an RP
The following sections describe the four recommended methods for configuring an RP in a PIM-SM network. Sample configurations are also provided for each scenario. Figure 1 shows the network topology used for the sample configurations.
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Figure 1 Network Topology Used for Sample Configurations
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Auto-RP with Multiple RPs Scenario
In this scenario, RP information is distributed to the routers by the Auto-RP mechanism. For more information about Auto-RP, see the "RP Configuration Overview" section earlier in this document. A prerequisite of Auto-RP is that all interfaces must be configured in PIM sparse-dense mode. For more information about using sparse-dense mode with Auto-RP, see the "Sparse-Dense Mode for Auto-RP" section earlier in this document.
In the following sample configuration, routers 72a and 75a are configured as both a candidate RP and RP mapping agent. At any given time, only one RP address is active (either per group or, as in the following sample configuration, for all groups).
Having multiple candidates for the role of RP and mapping agent greatly enhances the redundancy of the PIM-SM network. Redundancy reduces the risk of groups (configured in sparse-dense mode) reverting to dense mode operation if an RP cannot be located. To eliminate this risk, we recommend configuring a sink RP on every router in the network. In the following sample configuration, a sink RP with the fictitious address 1.1.1.1 is configured on all routers. For more information on sink RPs, see the "Sparse-Dense Mode for Auto-RP" section earlier in this document.
For the Auto-RP with Multiple RPs scenario, no load balancing is provided, and, when an RP changes, convergence is normally on the order of 3 minutes.
The following relevant multicast commands are used in this scenario:
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Configuration Files
Router 36a
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.6 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet2/0ip address 20.0.6.6 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36b
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.7 255.255.255.0ip pim sparse-dense-modeinterface Ethernet1/0ip address 20.0.10.7 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet2/0ip address 20.0.8.7 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36c
ip multicast-routinginterface Serial0/0ip address 20.0.9.10 255.255.255.0ip pim sparse-dense-modeinterface Ethernet0/1ip address 20.0.10.10 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet1/0ip address 20.0.3.10 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36d
ip multicast-routinginterface Serial0/0ip address 20.0.9.11 255.255.255.0ip pim sparse-dense-modeinterface Ethernet0/1ip address 20.0.5.11 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 72a
ip multicast-routinginterface Loopback0ip address 20.0.0.3 255.255.255.255ip pim sparse-dense-modeinterface FastEthernet0/0ip address 20.0.1.3 255.255.255.0ip pim sparse-dense-modeinterface Ethernet3/1ip address 20.0.3.3 255.255.255.0ip pim sparse-dense-modeinterface Ethernet3/2ip address 20.0.2.3 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20ip pim send-rp-announce Loopback0 scope 32 group-list 10ip pim send-rp-discovery Loopback0 scope 32access-list 10 permit 224.0.0.0 15.255.255.255access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 75a
ip multicast-routing distributedinterface Loopback0ip address 20.0.0.2 255.255.255.255ip pim sparse-dense-modeinterface FastEthernet0/0/0ip address 20.0.1.2 255.255.255.0ip pim sparse-dense-modeip route-cache distributedinterface FastEthernet0/1/0ip address 20.0.6.2 255.255.255.0ip pim sparse-dense-modeip route-cache distributedip pim rp-address 1.1.1.1 20ip pim send-rp-announce Loopback0 scope 32 group-list 10ip pim send-rp-discovery Loopback0 scope 32access-list 10 permit 224.0.0.0 15.255.255.255access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255The following example shows output from the show ip pim rp and show ip pim rp mapping commands. In this example, all groups are using 20.0.0.3 as the RP address. This address was chosen by the RP mapping agent because it was the highest IP address.
36b# show ip pim rpGroup: 224.128.1.1, RP: 20.0.0.3, v2, v1, uptime 00:03:01, expires 00:02:50The RP has now changed to 20.0.0.336b# show ip pim rp mappingPIM Group-to-RP MappingsGroup(s) 224.0.0.0/4RP 20.0.0.3 (?), v2v1Info source: 20.0.0.2 (?), via Auto-RPUptime: 00:22:08, expires: 00:02:40BSR with Multiple RPs Scenario
In this scenario, RP information is distributed to the routers by the BSR mechanism. For more information about the BSR mechanism, see the "RP Configuration Overview" section earlier in this document.
In the following sample configuration, routers 72a and 75a are configured as both a BSR candidate and an RP candidate. Having multiple candidates for the role of BSR and RP greatly enhances the redundancy of the PIM-SM network. At any given time, only one RP address is active (either per group or, as in the following sample configuration, for all groups).
For the BSR with Multiple RPs scenario, no load balancing is provided, and, when an RP changes, convergence is normally on the order of 3 minutes.
The following relevant multicast commands areused in this scenario:
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Configuration Files
Router 36a
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.6 255.255.255.0ip pim sparse-modeinterface FastEthernet2/0ip address 20.0.6.6 255.255.255.0ip pim sparse-modeRouter 36b
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.7 255.255.255.0ip pim sparse-modeinterface Ethernet1/0ip address 20.0.10.7 255.255.255.0ip pim sparse-modeinterface FastEthernet2/0ip address 20.0.8.7 255.255.255.0ip pim sparse-modeRouter 36c
ip multicast-routinginterface Serial0/0ip address 20.0.9.10 255.255.255.0ip pim sparse-modeinterface Ethernet0/1ip address 20.0.10.10 255.255.255.0ip pim sparse-modeRouter 36d
ip multicast-routinginterface Serial0/0ip address 20.0.9.11 255.255.255.0ip pim sparse-modeinterface Ethernet0/1ip address 20.0.5.11 255.255.255.0ip pim sparse-modeRouter 72a
ip multicast-routinginterface Loopback0ip address 20.0.0.3 255.255.255.255ip pim sparse-modeinterface FastEthernet0/0ip address 20.0.1.3 255.255.255.0ip pim sparse-modeinterface Ethernet3/1ip address 20.0.3.3 255.255.255.0ip pim sparse-modeinterface Ethernet3/2ip address 20.0.2.3 255.255.255.0ip pim sparse-modeip pim bsr-candidate Loopback0 1ip pim rp-candidate Loopback0Router 75a
ip multicast-routing distributedinterface Loopback0ip address 20.0.0.2 255.255.255.255ip pim sparse-modeinterface FastEthernet0/0/0ip address 20.0.1.2 255.255.255.0ip pim sparse-modeinterface FastEthernet0/1/0ip address 20.0.6.2 255.255.255.0ip pim sparse-modeip pim bsr-candidate Loopback0 1ip pim rp-candidate Loopback0The following example shows output from the show ip pim bsr command. The IP addresses of the two candidates for BSR are 20.0.0.2 and 20.0.0.3. The 20.0.0.3 address is chosen as the BSR because it is the higher IP address.
75a# show ip pim bsrPIMv2 Bootstrap informationBSR address: 20.0.0.3 (?)Uptime: 00:23:32, BSR Priority: 0, Hash mask length: 1Expires: 00:01:57This system is a candidate BSRCandidate BSR address: 20.0.0.2, priority: 0, hash mask length: 1Next C and_RP_advertisement in 00:00:18RP: 20.0.0.2(Loopback0)Anycast Static RP Scenario
In this scenario, Anycast RPs are configured statically and interfaces are configured to operate in PIM-SM. In Anycast RP, two or more RPs are configured with the "same" IP address on loopback interfaces. The Anycast RP loopback address should be configured with a 32-bit mask, making it a host address. This scenario is easy to configure and troubleshoot because the same host address is used as the RP address regardless of which router it is configured on.
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All the downstream routers should be configured to "know" that the Anycast RP loopback address is the IP address of their local RP. IP routing will automatically select the topologically closest RP for each source and receiver. Assuming that the sources are evenly distributed around the network, an equal number of sources will register with each RP. That is, the process of registering the sources will be shared equally by all the RPs in the network.
In the following sample configuration, routers 72a and 75a are configured as Anycast RPs. Because two routers are configured with the same RP address, there is not a single point of failure. At any given time, only one RP address is active (either per group or, as in the following sample configuration, for all groups).
Anycast RP provides excellent redundancy and load balancing. The load balancing is achieved through Multicast Source Discovery Protocol (MSDP), which allows RPs to exchange information about active sources.
For the Anycast Static RP scenario, when an RP changes, convergence is normally on the order of seconds.
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The following relevant multicast commands are used in this scenario:
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Configuration Files
Router 36a
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.6 255.255.255.0ip pim sparse-modeinterface FastEthernet2/0ip address 20.0.6.6 255.255.255.0ip pim sparse-modeip pim rp-address 20.0.0.1Router 36b
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.7 255.255.255.0ip pim sparse-modeinterface Ethernet1/0ip address 20.0.10.7 255.255.255.0ip pim sparse-modeinterface FastEthernet2/0ip address 20.0.8.7 255.255.255.0ip pim sparse-modeip pim rp-address 20.0.0.1Router 36c
ip multicast-routinginterface Serial0/0ip address 20.0.9.10 255.255.255.0ip pim sparse-modeinterface Ethernet0/1ip address 20.0.10.10 255.255.255.0ip pim sparse-modeinterface FastEthernet1/0ip address 20.0.3.10 255.255.255.0ip pim sparse-modeip pim rp-address 20.0.0.1Router 36d
ip multicast-routinginterface Serial0/0ip address 20.0.9.11 255.255.255.0ip pim sparse-modeinterface Ethernet0/1ip address 20.0.5.11 255.255.255.0ip pim sparse-modeip pim rp-address 20.0.0.1Router 72a
ip multicast-routinginterface Loopback0ip address 20.0.0.3 255.255.255.255ip pim sparse-modeinterface Loopback1ip address 20.0.0.1 255.255.255.255ip pim sparse-modeinterface FastEthernet0/0ip address 20.0.1.3 255.255.255.0ip pim sparse-modeinterface Ethernet3/1ip address 20.0.3.3 255.255.255.0ip pim sparse-modeinterface Ethernet3/2ip address 20.0.2.3 255.255.255.0ip pim sparse-modeip pim rp-address 20.0.0.1ip msdp peer 20.0.0.2 connect-source Loopback0ip msdp mesh-group anycast 20.0.0.2ip msdp originator-id Loopback0Router 75a
ip multicast-routing distributedinterface Loopback0ip address 20.0.0.2 255.255.255.255ip pim sparse-modeinterface Loopback1ip address 20.0.0.1 255.255.255.255ip pim sparse-modeinterface FastEthernet0/0/0ip address 20.0.1.2 255.255.255.0ip pim sparse-modeip route-cache distributedinterface FastEthernet0/1/0ip address 20.0.6.2 255.255.255.0ip pim sparse-modeip route-cache distributedip pim rp-address 20.0.0.1ip msdp peer 20.0.0.3 connect-source Loopback0ip msdp mesh-group anycast 20.0.0.3ip msdp originator-id Loopback0Anycast RP with Auto-RP Scenario
In this scenario, Anycast RP information is distributed to the routers by the Auto-RP mechanism. For more information about Anycast RP, see the "Anycast Static RP Scenario" section earlier in this document. For more information about Auto-RP, see the "RP Configuration Overview" section earlier in this document. A prerequisite of Auto-RP is that all interfaces must be configured in PIM sparse-dense mode. For more information about using sparse-dense mode with Auto-RP, see the "Sparse-Dense Mode for Auto-RP" section earlier in this document.
In the following sample configuration, routers 72a and 75a are configured as Anycast RPs. Because two routers are configured with the same RP address, there is not a single point of failure. At any given time, only one RP address is active (either per group or, as in the following sample configuration, for all groups).
Anycast RP provides excellent redundancy and load balancing. The load balancing is achieved through Multicast Source Discovery Protocol (MSDP), which allows RPs to exchange information about active sources. Redundancy reduces the risk of groups (configured in sparse-dense mode) reverting to dense mode operation if an RP cannot be located. To eliminate this risk, we recommend configuring a sink RP on every router in the network. In the following sample configuration, a sink RP with the fictitious address 1.1.1.1 is configured on all routers. For more information on sink RPs, see the "Sparse-Dense Mode for Auto-RP" section earlier in this document.
For the Anycast RP with Auto-RP scenario, when an RP changes, convergence is normally on the order of seconds.
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The following relevant multicast commands are used in this scenario:
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Configuration Files
Router 36a
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.6 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet2/0ip address 20.0.6.6 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36b
ip multicast-routinginterface Ethernet0/1ip address 20.0.7.7 255.255.255.0ip pim sparse-dense-modeinterface Ethernet1/0ip address 20.0.10.7 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet2/0ip address 20.0.8.7 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36c
ip multicast-routinginterface Serial0/0ip address 20.0.9.10 255.255.255.0ip pim sparse-dense-modeinterface Ethernet0/1ip address 20.0.10.10 255.255.255.0ip pim sparse-dense-modeinterface FastEthernet1/0ip address 20.0.3.10 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 36d
ip multicast-routinginterface Serial0/0ip address 20.0.9.11 255.255.255.0ip pim sparse-dense-mode!interface Ethernet0/1ip address 20.0.5.11 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 72a
ip multicast-routinginterface Loopback0ip address 20.0.0.3 255.255.255.255ip pim sparse-dense-modeinterface Loopback1ip address 20.0.0.1 255.255.255.255ip pim sparse-dense-modeinterface FastEthernet0/0ip address 20.0.1.3 255.255.255.0ip pim sparse-dense-modeinterface Ethernet3/1ip address 20.0.3.3 255.255.255.0ip pim sparse-dense-modeinterface Ethernet3/2ip address 20.0.2.3 255.255.255.0ip pim sparse-dense-modeip pim rp-address 1.1.1.1 20ip pim send-rp-announce Loopback1 scope 32 group-list 10ip pim send-rp-discovery Loopback1 scope 32ip msdp peer 20.0.0.2 connect-source Loopback0ip msdp mesh-group anycast 20.0.0.2ip msdp originator-id Loopback0access-list 10 permit 224.0.0.0 15.255.255.255access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Router 75a
ip multicast-routing distributedinterface Loopback0ip address 20.0.0.2 255.255.255.255ip pim sparse-dense-modeinterface Loopback1ip address 20.0.0.1 255.255.255.255ip pim sparse-dense-modeinterface FastEthernet0/0/0ip address 20.0.1.2 255.255.255.0ip pim sparse-dense-modeip route-cache distributedinterface FastEthernet0/1/0ip address 20.0.6.2 255.255.255.0ip pim sparse-dense-modeip route-cache distributedip pim rp-address 1.1.1.1 20ip pim send-rp-announce Loopback1 scope 32 group-list 10ip pim send-rp-discovery Loopback1 scope 32ip msdp peer 20.0.0.3 connect-source Loopback0ip msdp mesh-group anycast 20.0.0.3ip msdp originator-id Loopback0access-list 10 permit 224.0.0.0 15.255.255.255access-list 20 deny 224.0.1.39access-list 20 deny 224.0.1.40access-list 20 permit 224.0.0.0 15.255.255.255Related Documents
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http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/mcst_sol/anycast.htm
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http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/mcst_sol/mcst_ovr.htm
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http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/index.htm
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http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprmc_r/index.htm
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http://www.cisco.com/go/ipmulticast
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ftp://ftpeng.cisco.com/ipmulticast.html
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