IP Multicast: PIM Configuration Guide, Cisco IOS XE Release 3S
Configuring Basic IP Multicast
Downloads: This chapterpdf (PDF - 1.52MB) The complete bookPDF (PDF - 5.1MB) | The complete bookePub (ePub - 1.1MB) | Feedback

Configuring Basic IP Multicast

Contents

Configuring Basic IP Multicast

IP multicast is a bandwidth-conserving technology that reduces traffic by delivering a single stream of information simultaneously to potentially thousands of corporate businesses and homes. Applications that take advantage of multicast include video conferencing, corporate communications, distance learning, and distribution of software, stock quotes, and news. This module describes the tasks used to configure basic IP multicast.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Configuring Basic IP Multicast

  • To determine which of the tasks contained in this module you will have to perform, you must decide which Protocol Independent Multicast (PIM) mode will be used. This determination is based on the applications you intend to support on your network.
  • All access lists to be used with the tasks in this module should be configured prior to beginning the configuration task. For information about how to configure an access list, see the “Creating an IP Access List and Applying It to an Interface” module of the Security Configuration Guide: Access Control Lists guide.

Information About Configuring Basic IP Multicast

Auto-RP Overview

The Role of AutoRP in a PIM Network

AutoRP automates the distribution of group-to-rendezvous point (RP) mappings in a PIM network. To make AutoRP 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 AutoRP.

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.

IP Multicast Boundary

As shown in the figure, address scoping defines domain boundaries so that domains with RPs that have the same IP address do not leak into each other. Scoping is performed on the subnet boundaries within large domains and on the boundaries between the domain and the Internet.

Figure 1. Address Scoping at Boundaries

You can set up an administratively scoped boundary on an interface for multicast group addresses using the ip multicast boundary command with the access-list argument. A standard access list defines the range of addresses affected. When a boundary is set up, no multicast data packets are allowed to flow across the boundary from either direction. The boundary allows the same multicast group address to be reused in different administrative domains.

The Internet Assigned Numbers Authority (IANA) has designated the multicast address range 239.0.0.0 to 239.255.255.255 as the administratively scoped addresses. This range of addresses can be reused in domains administered by different organizations. They would be considered local, not globally unique.

You can configure the filter-autorp keyword to examine and filter Auto-RP discovery and announcement messages at the administratively scoped boundary. Any Auto-RP group range announcements from the Auto-RP packets that are denied by the boundary access control list (ACL) are removed. An Auto-RP group range announcement is permitted and passed by the boundary only if all addresses in the Auto-RP group range are permitted by the boundary ACL. If any address is not permitted, the entire group range is filtered and removed from the Auto-RP message before the Auto-RP message is forwarded.

Benefits of Auto-RP in a PIM Network

  • Auto-RP allows any change to the RP designation to be configured only on the devices that are RPs, not on the leaf routers.
  • Auto-RP offers the ability to scope the RP address within a domain.

Anycast RP Overview

Anycast RP is a useful application of MSDP. Originally developed for interdomain multicast applications, MSDP used for Anycast RP is an intradomain feature that provides redundancy and load-sharing capabilities. Enterprise customers typically use Anycast RP for configuring a Protocol Independent Multicast sparse mode (PIM-SM) network to meet fault tolerance requirements within a single multicast domain.

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. All the downstream routers should be configured so 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 spaced 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.

Because a source may register with one RP and receivers may join to a different RP, a method is needed for the RPs to exchange information about active sources. This information exchange is done with MSDP.

In anycast RP, all the RPs are configured to be MSDP peers of each other. When a source registers with one RP, an SA message will be sent to the other RPs informing them that there is an active source for a particular multicast group. The result is that each RP will know about the active sources in the area of the other RPs. If any of the RPs were to fail, IP routing would converge, and one of the RPs would become the active RP in more than one area. New sources would register with the backup RP. Receivers would join the new RP and connectivity would be maintained.

The RP is normally needed only to start new sessions with sources and receivers. The RP facilitates the shared tree so that sources and receivers can establish a direct multicast data flow. If a multicast data flow is already established between a source and the receiver, an RP failure will not affect that session. Anycast RP ensures that new sessions with sources and receivers can begin at any time.

BSR Overview

BSR Election and Functionality

PIM uses the BSR to discover and announce RP-set information for each group prefix to all the routers in a PIM domain. This is the same function performed by Auto-RP, but the BSR is part of the PIM Version 2 specification. The BSR mechanism interoperates with Auto-RP on Cisco routers.

To avoid a single point of failure, you can configure several candidate BSRs in a PIM domain. A BSR is elected among the candidate BSRs automatically; they use bootstrap messages to discover which BSR has the highest priority. This router then announces to all PIM routers in the PIM domain that it is the BSR.

Following the election of the BSR, candidate RPs use unicast to announce to the BSR their willingness to be the RP. The BSR advertises the entire group-to-RP mapping set to the router link local address 224.0.0.13. Unlike the RP mapping agent in Auto-RP, which is used by Auto-RP to select the RP, every router in the BSR network is responsible for selecting the RP.

BSR lacks the ability to scope RP advertisements; however, BSR is used when vendor interoperability or open standard adherence is a requirement.

BSR Border Interface

A border interface in a PIM sparse mode domain requires precautions to prevent exchange of certain traffic with a neighboring domain reachable through that interface, especially if that domain is also running PIM sparse mode. BSR and Auto-RP messages should not be exchanged between different domains, because routers in one domain may elect RPs in the other domain, resulting in protocol malfunction or loss of isolation between the domains. Configure a BSR border interface to prevent BSR messages from being sent or received through an interface.

Static RP Overview

If you are configuring PIM sparse mode, you must configure a PIM RP for a multicast group. An RP can either be configured statically in each device, or learned through a dynamic mechanism. This task explains how to statically configure an RP, as opposed to the router learning the RP through a dynamic mechanism such as Auto-RP.

PIM designated routers (DRs) forward data from directly connected multicast sources to the RP for distribution down the shared tree. Data is forwarded to the RP in one of two ways. It is encapsulated in register packets and unicast directly to the RP, or, if the RP has itself joined the source tree, it is multicast forwarded per the RPF forwarding algorithm. Last hop routers directly connected to receivers may, at their discretion, join themselves to the source tree and prune themselves from the shared tree.

A single RP can be configured for multiple groups that are defined by an access list. If no RP is configured for a group, the router treats the group as dense using the PIM dense mode techniques. (You can prevent this occurrence by configuring the no ip pim dm-fallbackcommand.)

If dynamic and static group-to-RP mappings are used together and there is an RP address conflict, the RP address configured for a static group-to-RP mapping (with the ip pim rp-address overridecommand) will take precedence.


Note


If the override keyword is not specified and there is RP address conflict, dynamic group-to-RP mappings will take precedence over static group-to-RP mappings.


SSM Overview

Source Specific Multicast (SSM). SSM is an extension of IP multicast where datagram traffic is forwarded to receivers from only those multicast sources that the receivers have explicitly joined. For multicast groups configured for SSM, only source-specific multicast distribution trees (not shared trees) are created.

SSM Components

Source Specific Multicast (SSM) is a datagram delivery model that best supports one-to-many applications, also known as broadcast applications. SSM is a core networking technology for the Cisco implementation of IP multicast solutions targeted for audio and video broadcast application environments and is described in RFC 3569. The following two components together support the implementation of SSM:

  • Protocol Independent Multicast source-specific mode (PIM-SSM)
  • Internet Group Management Protocol Version 3 (IGMPv3)

Protocol Independent Multicast (PIM) SSM, or PIM-SSM, is the routing protocol that supports the implementation of SSM and is derived from PIM sparse mode (PIM-SM). IGMP is the Internet Engineering Task Force (IETF) standards track protocol used for hosts to signal multicast group membership to routers. IGMP Version 3 supports source filtering, which is required for SSM. In order for SSM to run with IGMPv3, SSM must be supported in the device, the host where the application is running, and the application itself.

How SSM Differs from Internet Standard Multicast

The standard IP multicast infrastructure in the Internet and many enterprise intranets is based on the PIM-SM protocol and Multicast Source Discovery Protocol (MSDP). These protocols have proved to be reliable, extensive, and efficient. However, they are bound to the complexity and functionality limitations of the Internet Standard Multicast (ISM) service model. For example, with ISM, the network must maintain knowledge about which hosts in the network are actively sending multicast traffic. With SSM, this information is provided by receivers through the source addresses relayed to the last-hop devices by IGMPv3. SSM is an incremental response to the issues associated with ISM and is intended to coexist in the network with the protocols developed for ISM. In general, SSM provides IP multicast service for applications that utilize SSM.

ISM service is described in RFC 1112. This service consists of the delivery of IP datagrams from any source to a group of receivers called the multicast host group. The datagram traffic for the multicast host group consists of datagrams with an arbitrary IP unicast source address S and the multicast group address G as the IP destination address. Systems will receive this traffic by becoming members of the host group. Membership in a host group simply requires signaling the host group through IGMP Version 1, 2, or 3.

In SSM, delivery of datagrams is based on (S, G) channels. Traffic for one (S, G) channel consists of datagrams with an IP unicast source address S and the multicast group address G as the IP destination address. Systems will receive this traffic by becoming members of the (S, G) channel. In both SSM and ISM, no signaling is required to become a source. However, in SSM, receivers must subscribe or unsubscribe to (S, G) channels to receive or not receive traffic from specific sources. In other words, receivers can receive traffic only from (S, G) channels to which they are subscribed, whereas in ISM, receivers need not know the IP addresses of sources from which they receive their traffic. The proposed standard approach for channel subscription signaling utilizes IGMP INCLUDE mode membership reports, which are supported only in IGMP Version 3.

SSM can coexist with the ISM service by applying the SSM delivery model to a configured subset of the IP multicast group address range. The Internet Assigned Numbers Authority (IANA) has reserved the address range from 232.0.0.0 through 232.255.255.255 for SSM applications and protocols. The software allows SSM configuration for an arbitrary subset of the IP multicast address range from 224.0.0.0 through 239.255.255.255. When an SSM range is defined, an existing IP multicast receiver application will not receive any traffic when it tries to use addresses in the SSM range unless the application is modified to use explicit (S, G) channel subscription or is SSM-enabled through a URL Rendezvous Directory (URD).

SSM Operations

An established network in which IP multicast service is based on PIM-SM can support SSM services. SSM can also be deployed alone in a network without the full range of protocols that are required for interdomain PIM-SM. That is, SSM does not require an RP, so there is no need for an RP mechanism such as Auto-RP, MSDP, or bootstrap router (BSR).

If SSM is deployed in a network that is already configured for PIM-SM, then only the last-hop devices must be upgraded to a software image that supports SSM. Routers that are not directly connected to receivers do not have to upgrade to a software image that supports SSM. In general, these non-last-hop devices must only run PIM-SM in the SSM range. They may need additional access control configuration to suppress MSDP signaling, registering, or PIM-SM shared-tree operations from occurring within the SSM range.

The SSM mode of operation is enabled by configuring the SSM range using the ip pim ssm global configuration command. This configuration has the following effects:

  • For groups within the SSM range, (S, G) channel subscriptions are accepted through IGMPv3 INCLUDE mode membership reports.
  • PIM operations within the SSM range of addresses change to PIM-SSM, a mode derived from PIM-SM. In this mode, only PIM (S, G) Join and Prune messages are generated by the device. Incoming messages related to rendezvous point tree (RPT) operations are ignored or rejected, and incoming PIM register messages are immediately answered with Register-Stop messages. PIM-SSM is backward-compatible with PIM-SM unless a device is a last-hop device. Therefore, devices that are not last-hop devices can run PIM-SM for SSM groups (for example, if they do not yet support SSM).
  • For groups within the SSM range, no MSDP Source-Active (SA) messages within the SSM range will be accepted, generated, or forwarded.

IGMPv3 Host Signaling

IGMPv3 is the third version of the IETF standards track protocol in which hosts signal membership to last-hop devices of multicast groups. IGMPv3 introduces the ability for hosts to signal group membership that allows filtering capabilities with respect to sources. A host can signal either that it wants to receive traffic from all sources sending to a group except for some specific sources (a mode called EXCLUDE) or that it wants to receive traffic only from some specific sources sending to the group (a mode called INCLUDE).

IGMPv3 can operate with both ISM and SSM. In ISM, both EXCLUDE and INCLUDE mode reports are accepted by the last-hop router. In SSM, only INCLUDE mode reports are accepted by the last-hop router.

Benefits of Source Specific Multicast

IP Multicast Address Management Not Required

In the ISM service, applications must acquire a unique IP multicast group address because traffic distribution is based only on the IP multicast group address used. If two applications with different sources and receivers use the same IP multicast group address, then receivers of both applications will receive traffic from the senders of both applications. Even though the receivers, if programmed appropriately, can filter out the unwanted traffic, this situation would cause generally unacceptable levels of unwanted traffic.

Allocating a unique IP multicast group address for an application is still a problem. Most short-lived applications use mechanisms like Session Description Protocol (SDP) and Session Announcement Protocol (SAP) to get a random address, a solution that does not work well with a rising number of applications in the Internet. The best current solution for long-lived applications is described in RFC 2770, but this solution suffers from the restriction that each autonomous system is limited to only 255 usable IP multicast addresses.

In SSM, traffic from each source is forwarded between devices in the network independent of traffic from other sources. Thus different sources can reuse multicast group addresses in the SSM range.

Denial of Service Attacks from Unwanted Sources Inhibited

In SSM, multicast traffic from each individual source will be transported across the network only if it was requested (through IGMPv3, IGMP v3lite, or URD memberships) from a receiver. In contrast, ISM forwards traffic from any active source sending to a multicast group to all receivers requesting that multicast group. In Internet broadcast applications, this ISM behavior is highly undesirable because it allows unwanted sources to easily disturb the actual Internet broadcast source by simply sending traffic to the same multicast group. This situation depletes bandwidth at the receiver side with unwanted traffic and thus disrupts the undisturbed reception of the Internet broadcast. In SSM, this type of denial of service (DoS) attack cannot be made by simply sending traffic to a multicast group.

Easy to Install and Manage

SSM is easy to install and provision in a network because it does not require the network to maintain which active sources are sending to multicast groups. This requirement exists in ISM (with IGMPv1, IGMPv2, or IGMPv3).

The current standard solutions for ISM service are PIM-SM and MSDP. Rendezvous point (RP) management in PIM-SM (including the necessity for Auto-RP or BSR) and MSDP is required only for the network to learn about active sources. This management is not necessary in SSM, which makes SSM easier than ISM to install and manage, and therefore easier than ISM to operationally scale in deployment. Another factor that contributes to the ease of installation of SSM is the fact that it can leverage preexisting PIM-SM networks and requires only the upgrade of last hop devices to support IGMPv3, IGMP v3lite, or URD.

Ideal for Internet Broadcast Applications

The three benefits previously described make SSM ideal for Internet broadcast-style applications for the following reasons:

  • The ability to provide Internet broadcast services through SSM without the need for unique IP multicast addresses allows content providers to easily offer their service (IP multicast address allocation has been a serious problem for content providers in the past).
  • The prevention against DoS attacks is an important factor for Internet broadcast services because, with their exposure to a large number of receivers, they are the most common targets for such attacks.
  • The ease of installation and operation of SSM makes it ideal for network operators, especially in those cases where content needs to be forwarded between multiple independent PIM domains (because there is no need to manage MSDP for SSM between PIM domains).

Bidir-PIM Overview

Bidir-PIM shares many of its shortest path tree (SPT) operations with PIM-SM. Bidir-PIM also has unconditional forwarding of source traffic toward the RP upstream on the shared tree, but has no registering process for sources as in PIM-SM. These modifications allow forwarding of traffic in all routers based solely on the (*, G) multicast routing entries. This form of forwarding eliminates any source-specific state and allows scaling capability to an arbitrary number of sources.

Multicast Group Modes

In PIM, packet traffic for a multicast group is routed according to the rules of the mode configured for that multicast group. The Cisco implementation of PIM supports four modes for a multicast group:

  • PIM bidirectional mode
  • PIM dense mode
  • PIM sparse mode
  • PIM Source Specific Mode (SSM)

A router can simultaneously support all four modes or any combination of them for different multicast groups.

Bidirectional Shared Tree

In bidirectional mode, traffic is routed only along a bidirectional shared tree that is rooted at the rendezvous point (RP) for the group. In bidir-PIM, the IP address of the RP acts as the key to having all routers establish a loop-free spanning tree topology rooted in that IP address. This IP address need not be a router, but can be any unassigned IP address on a network that is reachable throughout the PIM domain. This technique is the preferred configuration method for establishing a redundant RP configuration for bidir-PIM.

Membership in a bidirectional group is signaled by way of explicit Join messages. Traffic from sources is unconditionally sent up the shared tree toward the RP and passed down the tree toward the receivers on each branch of the tree.

The figures below show the difference in state created per router for a unidirectional shared tree and source tree versus a bidirectional shared tree.

Figure 2. Unidirectional Shared Tree and Source Tree

Figure 3. Bidirectional Shared Tree

For packets that are forwarded downstream from the RP toward receivers, there are no fundamental differences between bidir-PIM and PIM-SM. Bidir-PIM deviates substantially from PIM-SM for traffic that is passed from sources upstream toward the RP.

PIM-SM cannot forward traffic in the upstream direction of a tree because it accepts traffic from only one Reverse Path Forwarding (RPF) interface. This interface (for the shared tree) points toward the RP, thus allowing only downstream traffic flow. Upstream traffic is first encapsulated into unicast register messages, which are passed from the designated router (DR) of the source toward the RP. Second, the RP joins an SPT that is rooted at the source. Therefore, in PIM-SM, traffic from sources destined for the RP does not flow upstream in the shared tree, but downstream along the SPT of the source until it reaches the RP. From the RP, traffic flows along the shared tree toward all receivers.

In bidir-PIM, the packet-forwarding rules have been improved over PIM-SM, allowing traffic to be passed up the shared tree toward the RP. To avoid multicast packet looping, bidir-PIM introduces a new mechanism called designated forwarder (DF) election, which establishes a loop-free SPT rooted at the RP.

DF Election

On every network segment and point-to-point link, all PIM routers participate in a procedure called designated forwarder (DF) election. The procedure selects one router as the DF for every RP of bidirectional groups. This router is responsible for forwarding multicast packets received on that network.

The DF election is based on unicast routing metrics. The router with the most preferred unicast routing metric to the RP becomes the DF. Use of this method ensures that only one copy of every packet will be sent to the RP, even if there are parallel equal-cost paths to the RP.

A DF is selected for every RP of bidirectional groups. As a result, multiple routers may be elected as DF on any network segment, one for each RP. Any particular router may be elected as DF on more than one interface.

Bidirectional Group Tree Building

The procedure for joining the shared tree of a bidirectional group is almost identical to that used in PIM-SM. One main difference is that, for bidirectional groups, the role of the DR is assumed by the DF for the RP.

On a network that has local receivers, only the router elected as the DF populates the outgoing interface list (olist) upon receiving Internet Group Management Protocol (IGMP) Join messages, and sends (*, G) Join and Leave messages upstream toward the RP. When a downstream router wishes to join the shared tree, the RPF neighbor in the PIM Join and Leave messages is always the DF elected for the interface that lead to the RP.

When a router receives a Join or Leave message, and the router is not the DF for the receiving interface, the message is ignored. Otherwise, the router updates the shared tree in the same way as in sparse mode.

In a network where all routers support bidirectional shared trees, (S, G) Join and Leave messages are ignored. There is also no need to send PIM assert messages because the DF election procedure eliminates parallel downstream paths from any RP. An RP never joins a path back to the source, nor will it send any register stops.

Packet Forwarding

A router creates (*, G) entries only for bidirectional groups. The olist of a (*, G) entry includes all the interfaces for which the router has been elected DF and that have received either an IGMP or PIM Join message. If a router is located on a sender-only branch, it will also create a (*, G) state, but the olist will not include any interfaces.

If a packet is received from the RPF interface toward the RP, the packet is forwarded downstream according to the olist of the (*, G) entry. Otherwise, only the router that is the DF for the receiving interface forwards the packet upstream toward the RP; all other routers must discard the packet.

Benefits of Bidirectional PIM

  • Bidir-PIM removes the performance cost of maintaining a routing state table for a large number of sources.
  • Bidir-PIM is designed to be used for many-to-many applications within individual PIM domains. Multicast groups in bidirectional PIM mode can scale to an arbitrary number of sources without incurring overhead due to the number of sources.

How to Configure Basic IP Multicast

The tasks described in this section configure the basic IP multicast modes. No single task in this section is required; however, at least one of the tasks must be performed to configure IP multicast in a network. More than one of the tasks may be needed.

Configuring Sparse Mode with AutoRP

Before You Begin
  • An interface configured in sparse-dense mode is treated in either sparse mode or dense mode of operation, depending on the mode in which the multicast group operates. You must decide how to configure your interfaces.
  • All access lists that are needed when AutoRP is configured should be configured prior to beginning the configuration task.

Note


  • If a group has no known RP and the interface is configured to be sparse-dense mode, the interface is treated as if it were in dense mode, and data is flooded over the interface. To avoid this data flooding, configure the AutoRP listener and then configure the interface as sparse mode.
  • When configuring AutoRP, you must either configure the AutoRP listener feature (Step 5) and specify sparse mode (Step 7) or specify sparse-dense mode (Step 8) .
  • When you configure sparse-dense mode, dense mode failover may result in a network dense-mode flood. To avoid this condition, use PIM sparse mode with the AutoRP listener feature.

Follow this procedure to configure auto-rendezvous point (AutoRP). AutoRP can also be optionally used with anycast RP.
SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ip multicast-routing [distributed]

    4.    Either perform Steps 5 through 7 or perform Steps 6 and 8.

    5.    ip pim autorp listener

    6.    interface type number

    7.    ip pim sparse-mode

    8.    ip pim sparse-dense-mode

    9.    exit

    10.    Repeat Steps 1 through 9 on all PIM interfaces.

    11.    ip pim send-rp-announce {interface-type interface-number | ip-address} scope ttl-value [group-list access-list] [interval seconds] [bidir]

    12.    ip pim send-rp-discovery [interface-type interface-number] scope ttl-value [interval seconds]

    13.    ip pim rp-announce-filter rp-list access-list group-list access-list

    14.    no ip pim dm-fallback

    15.    interface type number

    16.    ip multicast boundary access-list [filter-autorp]

    17.    end

    18.    show ip pim autorp

    19.    show ip pim rp [mapping] [rp-address]

    20.    show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]

    21.    show ip mroute [group-address | group-name] [source-address | source-name] [interface-type interface-number] [summary] [count] [active kbps]


DETAILED STEPS
      Command or Action Purpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 ip multicast-routing [distributed]


    Example:
    Device(config)# ip multicast-routing
     

    Enables IP multicast routing.

    • Use the distributed keyword to enabled Multicast Distributed Switching.
     
    Step 4 Either perform Steps 5 through 7 or perform Steps 6 and 8.  

    --

     
    Step 5 ip pim autorp listener


    Example:
    Device(config)# ip pim autorp listener
     

    Causes IP multicast traffic for the two AutoRP groups 224.0.1.39 and 224.0.1.40 to be PIM dense mode flooded across interfaces operating in PIM sparse mode.

    • Skip this step if you are configuring sparse-dense mode in Step 8.
     
    Step 6 interface type number


    Example:
    Device(config)# interface Gigabitethernet 1/0/0
     

    Selects an interface that is connected to hosts on which PIM can be enabled.

     
    Step 7 ip pim sparse-mode


    Example:
    Device(config-if)# ip pim sparse-mode
     

    Enables PIM sparse mode on an interface. When configuring AutoRP in sparse mode, you must also configure the AutoRP listener in the next step.

    • Skip this step if you are configuring sparse-dense mode in Step 8.
     
    Step 8 ip pim sparse-dense-mode


    Example:
    Device(config-if)# ip pim sparse-dense-mode
     

    Enables PIM sparse-dense mode on an interface.

    • Skip this step if you configured sparse mode in Step 7.
     
    Step 9 exit


    Example:
    Device(config-if)# exit
     

    Exits interface configuration mode and returns to global configuration mode.

     
    Step 10 Repeat Steps 1 through 9 on all PIM interfaces.  

    --

     
    Step 11 ip pim send-rp-announce {interface-type interface-number | ip-address} scope ttl-value [group-list access-list] [interval seconds] [bidir]


    Example:
    Device(config)# ip pim send-rp-announce loopback0 scope 31 group-list 5 
     

    Sends RP announcements out all PIM-enabled interfaces.

    • Perform this step on the RP device only.
    • Use the interface-typeand interface-number arguments to define which IP address is to be used as the RP address.
    • Use the ip-address argument to specify a directly connected IP address as the RP address.
    Note   

    If the ip-address argument is configured for this command, the RP-announce message will be sourced by the interface to which this IP address is connected (that is, the source address in the IP header of the RP-announce message is the IP address of that interface).

    • This example shows that the interface is enabled with a maximum of 31 hops. The IP address by which the device wants to be identified as RP is the IP address associated with loopback interface 0. Access list 5 describes the groups for which this device serves as RP.
     
    Step 12 ip pim send-rp-discovery [interface-type interface-number] scope ttl-value [interval seconds]


    Example:
    Device(config)# ip pim send-rp-discovery loopback 1 scope 31 
     

    Configures the device to be an RP mapping agent.

    • Perform this step on RP mapping agent devices or on combined RP/RP mapping agent devices.
    Note   

    AutoRP allows the RP function to run separately on one device and the RP mapping agent to run on one or multiple devices. It is possible to deploy the RP and the RP mapping agent on a combined RP/RP mapping agent device.

    • Use the optional interface-type and interface-number arguments to define which IP address is to be used as the source address of the RP mapping agent.
    • Use the scope keyword and ttl-value argument to specify the Time-to-Live (TTL) value in the IP header of AutoRP discovery messages.
    • Use the optional interval keyword and seconds argument to specify the interval at which AutoRP discovery messages are sent.
    Note   

    Lowering the interval at which AutoRP discovery messages are sent from the default value of 60 seconds results in more frequent floodings of the group-to-RP mappings. In some network environments, the disadvantages of lowering the interval (more control packet overhead) may outweigh the advantages (more frequent group-to-RP mapping updates).

    • The example shows limiting the AutoRP discovery messages to 31 hops on loopback interface 1.
     
    Step 13 ip pim rp-announce-filter rp-list access-list group-list access-list


    Example:
    Device(config)# ip pim rp-announce-filter rp-list 1 group-list 2
     

    Filters incoming RP announcement messages sent from candidate RPs (C-RPs) to the RP mapping agent.

    • Perform this step on the RP mapping agent only.
     
    Step 14 no ip pim dm-fallback


    Example:
    Device(config)# no ip pim dm-fallback
     

    (Optional) Prevents PIM dense mode fallback.

    • Skip this step if all interfaces have been configured to operate in PIM sparse mode.
    Note   

    The no ip pim dm-fallback command behavior is enabled by default if all the interfaces are configured to operate in PIM sparse mode (using the ip pim sparse-mode command).

     
    Step 15 interface type number


    Example:
    Device(config)# interface gigabitethernet 1/0/0
     

    Selects an interface that is connected to hosts on which PIM can be enabled.

     
    Step 16 ip multicast boundary access-list [filter-autorp]


    Example:
    Device(config-if)# ip multicast boundary 10 filter-autorp
     

    Configures an administratively scoped boundary.

    • Perform this step on the interfaces that are boundaries to other devices.
    • The access list is not shown in this task.
    • An access list entry that uses the deny keyword creates a multicast boundary for packets that match that entry.
     
    Step 17 end


    Example:
    Device(config-if)# end
     

    Returns to global configuration mode.

     
    Step 18 show ip pim autorp


    Example:
    Device# show ip pim autorp
     

    (Optional) Displays the AutoRP information.

     
    Step 19 show ip pim rp [mapping] [rp-address]


    Example:
    Device# show ip pim rp mapping
     

    (Optional) Displays RPs known in the network and shows how the device learned about each RP.

     
    Step 20 show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]


    Example:
    Device# show ip igmp groups
     

    (Optional) Displays the multicast groups having receivers that are directly connected to the device and that were learned through Internet Group Management Protocol (IGMP).

    • A receiver must be active on the network at the time that this command is issued in order for receiver information to be present on the resulting display.
     
    Step 21 show ip mroute [group-address | group-name] [source-address | source-name] [interface-type interface-number] [summary] [count] [active kbps]


    Example:
    Device# show ip mroute cbone-audio 
     

    (Optional) Displays the contents of the IP multicast routing (mroute) table.

     

    What to Do Next

    Proceed to the “ Verifying IP Multicast Operation ” module.

    Configuring Sparse Mode with Anycast RP

    This section describes how to configure sparse mode with anycast RP for RP redundancy.

    Anycast RPs are configured statically, and interfaces are configured to operate in Protocol Independent Multicast-Sparse Mode (PIM-SM). In an anycast RP configuration, 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. An Anycast RP configuration 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.

    Anycast RP allows two or more rendezvous points (RPs) to share the load for source registration and have the ability to act as hot backup routers for each other. Multicast Source Discovery Protocol (MSDP) is the key protocol that makes anycast RP possible.

    Figure 4. MSDP Sharing Source Information Between RPs in Each Domain

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ip multicast-routing [distributed]

      4.    interface type number

      5.    ip pim sparse-mode

      6.    ip pim rp-address rp-address

      7.    Repeat Steps 1 through 6 on two or more routers assigning the same RP address to each.

      8.    interface loopback [interface-number] ip address [ip-address] [mask]

      9.    interface loopback [interface-number] ip address [ip-address] [mask]

      10.    exit

      11.    ip msdp peer {peer-name | peer-address} [connect-source interface-type interface-number] [remote-as as-number]

      12.    ip msdp originator-id loopback [interface]

      13.    Repeat Steps 8 through 12 on the redundant RPs.


    DETAILED STEPS
        Command or Action Purpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 ip multicast-routing [distributed]


      Example:
      Router(config)# ip multicast-routing
       

      Enables IP multicast routing.

      • Use the distributed keyword to enable Multicast Distributed Switching.
       
      Step 4 interface type number


      Example:
      Router(config)# interface gigabitethernet 1/0/0
       

      Selects an interface that is connected to hosts on which PIM can be enabled.

       
      Step 5 ip pim sparse-mode


      Example:
      Router(config-if)# ip pim sparse-mode
       

      Enables sparse mode.

       
      Step 6 ip pim rp-address rp-address


      Example:
      Router(config-if)# ip pim rp-address 10.0.0.1 
       

      Configures the address of a PIM RP for a particular group.

       
      Step 7 Repeat Steps 1 through 6 on two or more routers assigning the same RP address to each.  

      --

       
      Step 8 interface loopback [interface-number] ip address [ip-address] [mask]


      Example:
      Router(config-if)# interface loopback 0 


      Example:
      ip address 10.0.0.1 255.255.255.255
       

      Configures the interface loopback IP address for the RP router.

      • Perform this step on the RP routers.
       
      Step 9 interface loopback [interface-number] ip address [ip-address] [mask]


      Example:
      Router(config-if)# interface loopback 1 


      Example:
      ip address 10.1.1.1 255.255.255.255
       

      Configures the interface loopback IP address for MSDP peering.

       
      Step 10 exit


      Example:
      Router(config-if)# exit
       

      Exits interface configuration mode and returns to global configuration mode.

       
      Step 11 ip msdp peer {peer-name | peer-address} [connect-source interface-type interface-number] [remote-as as-number]


      Example:
      Router(config)# ip msdp peer 10.1.1.2 connect-source loopback 1
       

      Configures an MSDP peer.

      • Perform this step on the RP routers.
       
      Step 12 ip msdp originator-id loopback [interface]


      Example:
      Router(config)# ip msdp originator-id loopback 1
       

      Allows an MSDP speaker that originates a SA message to use the IP address of the interface as the RP address in the SA message.

      • Perform this step on the RP routers.
       
      Step 13 Repeat Steps 8 through 12 on the redundant RPs.  

      --

       

      What to Do Next

      Proceed to the “ Verifying IP Multicast Operation ” module.

      Configuring Sparse Mode with a Bootstrap Router

      This section describes how to configure a bootstrap router (BSR), which provides a fault-tolerant, automated RP discovery and distribution mechanism so that routers learn the group-to-RP mappings dynamically.


      Note


      The simultaneous deployment of Auto-RP and BSR is not supported.


      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    ip multicast-routing [distributed]

        4.    interface type number

        5.    ip pim sparse-mode

        6.    end

        7.    Repeat Steps 1 through 6 on every multicast-enabled interface on every router.

        8.    ip pim bsr-candidate interface-type interface-number [hash-mask-length [priority]]

        9.    ip pim rp-candidate interface-type interface-number [group-list access-list] [interval seconds] [priority value]

        10.    Repeat Steps 8 through 10 on all RP and BSR routers.

        11.    interface type number

        12.    ip pim bsr-border

        13.    end

        14.    Repeat Steps 11 through 13 on all the routers that have boundary interfaces where the messages should not be sent or received.

        15.    show ip pim rp [mapping] [rp-address]

        16.    show ip pim rp-hash [group-address] [group-name]

        17.    show ip pim bsr-router

        18.    show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]

        19.    show ip mroute


      DETAILED STEPS
          Command or Action Purpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 ip multicast-routing [distributed]


        Example:
        Router(config)# ip multicast-routing
         

        Enables IP multicast routing.

        • Use the distributed keyword to enable Multicast Distributed Switching.
         
        Step 4 interface type number


        Example:
        Router(config)# interface gigabitethernet 1/0/0
         

        Selects an interface that is connected to hosts on which PIM can be enabled.

         
        Step 5 ip pim sparse-mode


        Example:
        Router(config-if)# ip pim sparse-mode
         

        Enables sparse mode.

         
        Step 6 end


        Example:
        Router(config-if)# end
         

        Returns to global configuration mode.

         
        Step 7 Repeat Steps 1 through 6 on every multicast-enabled interface on every router. 

        --

         
        Step 8 ip pim bsr-candidate interface-type interface-number [hash-mask-length [priority]]


        Example:
        Router(config)# ip pim bsr-candidate gigibitethernet 0/0/0 0 192 
         

        Configures the router to announce its candidacy as a bootstrap router (BSR).

        • Perform this step on the RP or on combined RP/BSR routers.
        Note   

        BSR allows the RP function to run separately on one router and the BSR to run on one or multiple routers. It is possible to deploy the RP and the BSR on a combined RP/BSR router.

        • This command configures the router to send BSR messages to all its PIM neighbors, with the address of the designated interface (configured for the interface-type and interface-numberarguments) as the BSR address.
        • Use the optional hash-mask-length argument to set the length of a mask (32 bits maximum) that is to be ANDed with the group address before the PIMv2 hash function is called. All groups with the same seed hash (correspond) to the same RP. For example, if this value is 24, only the first 24 bits of the group addresses matter. The hash mask length allows one RP to be used for multiple groups. The default hash mask length is 0.
        • Use the optional priority argument (after you set the hash mask length) to specify the priority of the BSR as a C-RP. The priority range is from 0 to 255. The BSR C-RP with the highest priority (the lowest priority value) is preferred. If the priority values are the same, the router with the higher IP address is preferred. The default priority value is 0.
        Note   

        The Cisco IOS and Cisco IOS XE implementation of PIM BSR uses the value 0 as the default priority for candidate RPs and BSRs. This implementation predates the draft-ietf-pim-sm-bsr IETF draft, the first IETF draft to specify 192 as the default priority value. The Cisco IOS and Cisco IOS XE implementation, thus, deviates from the IETF draft. To comply with the default priority value specified in the draft, you must explicitly set the priority value to 192.

         
        Step 9 ip pim rp-candidate interface-type interface-number [group-list access-list] [interval seconds] [priority value]


        Example:
        Router(config)# ip pim rp-candidate gigabitethernet 2/0/0 group-list 4 priority 192
         

        Configures the router to advertise itself as a PIM Version 2 candidate RP to the BSR.

        • Perform this step on the RP or on combined RP/BSR routers.
        Note   

        BSR allows the RP function to run separately on one router and the BSR to run on one or multiple routers. It is possible to deploy the RP and the BSR on a combined RP/BSR router.

        • When an interval is specified, the candidate RP advertisement interval is set to the number of seconds specified. The default interval is 60 seconds. Tuning this interval down can reduce the time required to fail over to a secondary RP at the expense of generating more PIMv2 messages.
        • The Cisco IOS and Cisco IOS XE implementation of PIM BSR selects an RP from a set of candidate RPs using a method that is incompatible with the specification in RFC 2362. See the BSR and RFC 2362 Interoperable Candidate RP Example section for a configuration workaround. See CSCdy56806 using the Cisco Bug Toolkit for more information.
        Note   

        The Cisco IOS and Cisco IOS XE implementation of PIM BSR uses the value 0 as the default priority for candidate RPs and BSRs. This implementation predates the draft-ietf-pim-sm-bsr IETF draft, the first IETF draft to specify 192 as the default priority value. The Cisco IOS and Cisco IOS XE implementation, thus, deviates from the IETF draft. To comply with the default priority value specified in the draft, you must explicitly set the priority value to 192.

         
        Step 10 Repeat Steps 8 through 10 on all RP and BSR routers. 

        --

         
        Step 11 interface type number


        Example:
        Router(config)# interface gigabitethernet 1/0/0
         

        Selects an interface that is connected to hosts on which PIM can be enabled.

         
        Step 12 ip pim bsr-border


        Example:
        Router(config-if)# ip pim bsr-border
         

        Prevents the bootstrap router (BSR) messages from being sent or received through an interface.

         
        Step 13 end


        Example:
        Router(config-if)# end
         

        Ends the current configuration session and returns to privileged EXEC mode.

         
        Step 14 Repeat Steps 11 through 13 on all the routers that have boundary interfaces where the messages should not be sent or received. 

        --

         
        Step 15 show ip pim rp [mapping] [rp-address]


        Example:
        Router# show ip pim rp
         

        (Optional) Displays active rendezvous points (RPs) that are cached with associated multicast routing entries.

         
        Step 16 show ip pim rp-hash [group-address] [group-name]


        Example:
        Router# show ip pim rp-hash 239.1.1.1
         

        (Optional) Displays which rendezvous point (RP) is being selected for a specified group.

         
        Step 17 show ip pim bsr-router


        Example:
        Router# show ip pim bsr-router
         

        (Optional) Displays the bootstrap router (BSR) information.

         
        Step 18 show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]


        Example:
        Router# show ip igmp groups
         

        (Optional) Displays the multicast groups having receivers that are directly connected to the router and that were learned through IGMP.

        • A receiver must be active on the network at the time that this command is issued in order for receiver information to be present on the resulting display.
         
        Step 19 show ip mroute


        Example:
        Router# show ip mroute cbone-audio 
         

        (Optional) Displays the contents of the IP mroute table.

         

        What to Do Next

        Proceed to the “ Verifying IP Multicast Operation ” module.

        Configuring Sparse Mode with a Single Static RP

        A rendezvous point (RP) is required in networks running Protocol Independent Multicast sparse mode (PIM-SM). In PIM-SM, traffic will be forwarded only to network segments with active receivers that have explicitly requested multicast data.

        This section describes how to configure sparse mode with a single static RP.

        Before You Begin

        All access lists that are needed when sparse mode is configured with a single static RP should be configured prior to beginning the configuration task.


        Note


        The same RP address cannot be used for both bidirectional and sparse mode PIM groups.


        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    ip multicast-routing [distributed]

          4.    interface type number

          5.    ip pim sparse-mode

          6.    Repeat Steps 1 through 5 on every interface that uses IP multicast.

          7.    exit

          8.    ip pim rp-address rp-address [access-list] [override]

          9.    end

          10.    show ip pim rp [mapping] [rp-address]

          11.    show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]

          12.    show ip mroute


        DETAILED STEPS
            Command or Action Purpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Router# configure terminal
           

          Enters global configuration mode.

           
          Step 3 ip multicast-routing [distributed]


          Example:
          Router(config)# ip multicast-routing
           

          Enables IP multicast routing.

          • Use the distributed keyword to enable Multicast Distributed Switching.
           
          Step 4 interface type number


          Example:
          Router(config)# interface gigabitethernet 1/0/0
           

          Selects an interface that is connected to hosts on which PIM can be enabled.

           
          Step 5 ip pim sparse-mode


          Example:
          Router(config-if)# ip pim sparse-mode
           

          Enables PIM on an interface. You must use sparse mode.

           
          Step 6 Repeat Steps 1 through 5 on every interface that uses IP multicast.  

          --

           
          Step 7 exit


          Example:
          Router(config-if)# exit
           

          Returns to global configuration mode.

           
          Step 8 ip pim rp-address rp-address [access-list] [override]


          Example:
          Router(config)# ip pim rp-address 192.168.0.0 
           

          Configures the address of a PIM RP for a particular group.

          • The optional access-list argument is used to specify the number or name a standard access list that defines the multicast groups to be statically mapped to the RP.
          Note   

          If no access list is defined, the RP will map to all multicast groups, 224/4.

          • The optional override keyword is used to specify that if dynamic and static group-to-RP mappings are used together and there is an RP address conflict, the RP address configured for a static group-to-RP mapping will take precedence.
          Note   

          If the override keyword is not specified and there is RP address conflict, dynamic group-to-RP mappings will take precedence over static group-to-RP mappings.

           
          Step 9 end


          Example:
          Router(config)# end
           

          Ends the current configuration session and returns to EXEC mode.

           
          Step 10 show ip pim rp [mapping] [rp-address]


          Example:
          Router# show ip pim rp mapping
           

          (Optional) Displays RPs known in the network and shows how the router learned about each RP.

           
          Step 11 show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]


          Example:
          Router# show ip igmp groups
           

          (Optional) Displays the multicast groups having receivers that are directly connected to the router and that were learned through IGMP.

          • A receiver must be active on the network at the time that this command is issued in order for receiver information to be present on the resulting display.
           
          Step 12 show ip mroute


          Example:
          Router# show ip mroute
           

          (Optional) Displays the contents of the IP mroute table.

           

          What to Do Next

          Proceed to the “ Verifying IP Multicast Operation ” module.

          Configuring Source Specific Multicast

          This section describes how to configure Source Specific Multicast (SSM).

          Before You Begin

          If you want to use an access list to define the SSM range, configure the access list before you reference the access list in the ip pim ssm command.

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    ip multicast-routing [distributed]

            4.    ip pim ssm {default | range access-list}

            5.    interface type number

            6.    ip pim sparse-mode

            7.    Repeat Steps 1 through 6 on every interface that uses IP multicast.

            8.    ip igmp version 3

            9.    Repeat Step 8 on all host-facing interfaces.

            10.    end

            11.    show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]

            12.    show ip mroute


          DETAILED STEPS
              Command or Action Purpose
            Step 1 enable


            Example:
            Device> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 configure terminal


            Example:
            Device# configure terminal
             

            Enters global configuration mode.

             
            Step 3 ip multicast-routing [distributed]


            Example:
            Device(config)# ip multicast-routing 
             

            Enables IP multicast routing.

            • Use the distributed keyword to enable Multicast Distributed Switching.
             
            Step 4 ip pim ssm {default | range access-list}


            Example:
            Device(config)# ip pim ssm default
             

            Configures SSM service.

            • The default keyword defines the SSM range access list as 232/8.
            • The range keyword specifies the standard IP access list number or name that defines the SSM range.
             
            Step 5 interface type number


            Example:
            Device(config)# interface gigabitethernet 1/0/0
             

            Selects an interface that is connected to hosts on which IGMPv3 can be enabled.

             
            Step 6 ip pim sparse-mode


            Example:
            Device(config-if)# ip pim sparse-mode
             

            Enables PIM on an interface. You must use sparse mode.

             
            Step 7 Repeat Steps 1 through 6 on every interface that uses IP multicast.  

            --

             
            Step 8 ip igmp version 3


            Example:
            Device(config-if)# ip igmp version 3
             

            Enables IGMPv3 on this interface. The default version of IGMP is set to Version 2. Version 3 is required by SSM.

             
            Step 9 Repeat Step 8 on all host-facing interfaces.  

            --

             
            Step 10 end


            Example:
            Device(config-if)# end
             

            Ends the current configuration session and returns to privileged EXEC mode.

             
            Step 11 show ip igmp groups [group-name | group-address| interface-type interface-number] [detail]


            Example:
            Device# show ip igmp groups
             

            (Optional) Displays the multicast groups having receivers that are directly connected to the device and that were learned through IGMP.

            • A receiver must be active on the network at the time that this command is issued in order for receiver information to be present on the resulting display.
             
            Step 12 show ip mroute


            Example:
            Device# show ip mroute
             

            (Optional) Displays the contents of the IP mroute table.

            • This command displays whether a multicast group is configured for SSM service or a source-specific host report has been received.
             

            What to Do Next

            Proceed to the “ Verifying IP Multicast Operation ” module.

            Configuring Bidirectional PIM

            This section describes how to configure bidirectional PIM (bidir-PIM).

            Before You Begin

            All access lists needed when configuring bidirectional PIM must be configured prior to beginning the configuration task.

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    ip multicast-routing [distributed]

              4.    interface type number

              5.    ip pim sparse-mode

              6.    exit

              7.    ip pim bidir-enable

              8.    ip pim rp-address rp-address [access-list] [override] bidir

              9.    end

              10.    Repeat Steps 2 through 9 on every multicast-enabled interface on every router.

              11.    show ip pim rp [mapping] [rp-address]

              12.    show ip mroute

              13.    show ip pim interface [type number] [df | count] [rp-address]


            DETAILED STEPS
                Command or Action Purpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3 ip multicast-routing [distributed]


              Example:
              Router(config)# ip multicast-routing
               

              Enables IP multicast routing.

              • Use the distributed keyword to enable Multicast Distributed Switching.
               
              Step 4 interface type number


              Example:
              Router(config)# interface gigabitethernet 1/0/0
               

              Selects an interface that is connected to hosts on which PIM can be enabled.

               
              Step 5 ip pim sparse-mode


              Example:
              Router(config-if)# ip pim sparse-mode
               

              Enables sparse mode.

               
              Step 6 exit


              Example:
              Router(config-if)# exit
               

              Returns to global configuration mode.

               
              Step 7 ip pim bidir-enable


              Example:
              Router(config)# ip pim bidir-enable
               

              Enables bidir-PIM on a router.

              • Perform this step on every router.
               
              Step 8 ip pim rp-address rp-address [access-list] [override] bidir


              Example:
              Router(config)# ip pim rp-address 10.0.1.1 45 bidir
               

              Configures the address of a PIM RP for a particular group.

              • Perform this step on every router.
              • This command defines the RP as bidirectional and defines the bidirectional group by way of the access list.
              • The optional override keyword is used to specify that if dynamic and static group-to-RP mappings are used together and there is an RP address conflict, the RP address configured for a static group-to-RP mapping will take precedence.
              Note   

              If the override keyword is not specified and there is RP address conflict, dynamic group-to-RP mappings will take precedence over static group-to-RP mappings.

               
              Step 9 end


              Example:
              Router(config-if)# end
               

              Exits interface configuration mode and returns to privileged EXEC mode.

               
              Step 10 Repeat Steps 2 through 9 on every multicast-enabled interface on every router. 

              --

               
              Step 11 show ip pim rp [mapping] [rp-address]


              Example:
              Router# show ip pim rp 
               

              (Optional) Displays active RPs that are cached with associated multicast routing entries.

               
              Step 12 show ip mroute


              Example:
              Router# show ip mroute
               

              (Optional) Displays the contents of the IP mroute table.

               
              Step 13 show ip pim interface [type number] [df | count] [rp-address]


              Example:
              Router# show ip pim interface 
               

              (Optional) Displays information about the elected DF for each RP of an interface, along with the unicast routing metric associated with the DF.

               

              Configuration Examples for Basic IP Multicast

              Example: Sparse Mode with AutoRP

              The following example configures sparse mode with AutoRP:

              ip multicast-routing 
              ip pim autorp listener 
              ip pim send-rp-announce Loopback0 scope 16 group-list 1 
              ip pim send-rp-discovery Loopback1 scope 16 
              no ip pim dm-fallback
              access-list 1 permit 239.254.2.0 0.0.0.255 
              access-list 1 permit 239.254.3.0 0.0.0.255
              .
              .
              .
              access-list 10 permit 224.0.1.39
              access-list 10 permit 224.0.1.40
              access-list 10 permit 239.254.2.0 0.0.0.255
              access-list 10 permit 239.254.3.0 0.0.0.255

              Sparse Mode with Anycast RP Example

              The main purpose of an Anycast RP implementation is that the downstream multicast routers will have just one address for an RP. The example given in the figure below shows how loopback interface 0 of the RPs (RP1 and RP2) is configured with the 10.0.0.1 IP address. If this 10.0.0.1 address is configured on all RPs as the address for loopback interface 0 and then configured as the RP address, IP routing will converge on the closest RP. This address must be a host route; note the 255.255.255.255 subnet mask.

              The downstream routers must be informed about the 10.0.0.1 RP address. In the figure below, the routers are configured statically with the ip pim rp-address 10.0.0.1global configuration command. This configuration could also be accomplished using the Auto-RP or bootstrap router (BSR) features.

              The RPs in the figure must also share source information using MSDP. In this example, loopback interface 1 of the RPs (RP1 and RP2) is configured for MSDP peering. The MSDP peering address must be different from the anycast RP address.

              Figure 5. AnyCast RP Configuration

              Many routing protocols choose the highest IP address on loopback interfaces for the router ID. A problem may arise if the router selects the anycast RP address for the router ID. It is recommended that you avoid this problem by manually setting the router ID on the RPs to the same address as the MSDP peering address (for example, the loopback 1 address in the figure above). In Open Shortest Path First (OSPF), the router ID is configured using the router-idrouter configuration command. In Border Gateway Protocol (BGP), the router ID is configured using the bgp router-id router configuration command. In many BGP topologies, the MSDP peering address and the BGP peering address must be the same in order to pass the RPF check. The BGP peering address can be set using the neighbor update-source router configuration command.

              The anycast RP example above uses IP addresses taken from RFC 1918. These IP addresses are normally blocked at interdomain borders and therefore are not accessible to other ISPs. You must use valid IP addresses if you want the RPs to be reachable from other domains.

              The following example shows how to perform an Anycast RP configuration.

              On RP 1

              ip pim rp-address 10.0.0.1
              interface loopback 0
               ip address 10.0.0.1 255.255.255.255
              !
              interface loopback 1
               ip address 10.1.1.1. 255.255.255.255
              !
               ip msdp peer 10.1.1.2 connect-source loopback 1
               ip msdp originator-id loopback 1
              

              On RP 2

              ip pim rp-address 10.0.0.1
              interface loopback 0
               ip address 10.0.0.1 255.255.255.255
              interface loopback 1
               ip address 10.1.1.2. 255.255.255.255
              !
               ip msdp peer 10.1.1.1 connect-source loopback 1
               ip msdp originator-id loopback 1
              

              All Other Routers

              ip pim rp-address 10.0.0.1

              Sparse Mode with Bootstrap Router Example

              The following example is a configuration for a candidate BSR, which also happens to be a candidate RP:

              ! 
              ip multicast-routing 
              ! 
              interface GigabitEthernet0/0/0 
               ip address 172.69.62.35 255.255.255.240 
               ip pim sparse-mode 
              ! 
              interface GigabitEthernet1/0/0 
               ip address 172.21.24.18 255.255.255.248 
               ip pim sparse-mode 
              ! 
              interface GigabitEthernet2/0/0 
               ip address 172.21.24.12 255.255.255.248 
               ip pim sparse-mode 
              ! 
              ip pim bsr-candidate GigabitEthernet2/0/0 30 10 
              ip pim rp-candidate GigabitEthernet2/0/0 group-list 5 
              access-list 5 permit 239.255.2.0 0.0.0.255 

              BSR and RFC 2362 Interoperable Candidate RP Example

              When Cisco and non-Cisco routers are being operated in a single PIM domain with PIM Version 2 BSR, care must be taken when configuring candidate RPs because the Cisco implementation of the BSR RP selection is not fully compatible with RFC 2362.

              RFC 2362 specifies that the BSR RP be selected as follows (RFC 2362, 3.7):

              1. Select the candidate RP with the highest priority (lowest configured priority value).
              2. If there is a tie in the priority level, select the candidate RP with the highest hash function value.
              3. If there is a tie in the hash function value, select the candidate RP with the highest IP address.

              Cisco routers always select the candidate RP based on the longest match on the announced group address prefix before selecting an RP based on priority, hash function, or IP address.

              Inconsistent candidate RP selection between Cisco and non-Cisco RFC 2362-compliant routers in the same domain if multiple candidate RPs with partially overlapping group address ranges are configured can occur. Inconsistent candidate RP selection can prevent connectivity between sources and receivers in the PIM domain. A source may register with one candidate RP and a receiver may connect to a different candidate RP even though it is in the same group.

              The following example shows a configuration that can cause inconsistent RP selection between a Cisco and a non-Cisco router in a single PIM domain with PIM Version 2 BSR:

              access-list 10 permit 224.0.0.0  7.255.255.255 
              ip pim rp-candidate gigabitethernet1/0/0 group-list 10 priority 20
              access-list 20 permit 224.0.0.0 15.255.255.255
              ip pim rp-candidate gigabitethernet2/0/0 group-list 20 priority 10

              In this example, a candidate RP on GigabitEthernet interface 1/0/0 announces a longer group prefix of 224.0.0.0/5 with a lower priority of 20. The candidate RP on GigabitEthernet interface 2/0/0 announces a shorter group prefix of 224.0.0.0/4 with a higher priority of 10. For all groups that match both ranges a Cisco router will always select the candidate RP on Ethernet interface 1 because it has the longer announced group prefix. A non-Cisco fully RFC 2362-compliant router will always select the candidate RP on GigabitEthernet interface 2/0/0 because it is configured with a higher priority.

              To avoid this interoperability issue, do not configure different candidate RPs to announce partially overlapping group address prefixes. Configure any group prefixes that you want to announce from more than one candidate RP with the same group prefix length.

              The following example shows how to configure the previous example so that there is no incompatibility between a Cisco router and a non-Cisco router in a single PIM domain with PIM Version 2 BSR:

              access-list 10 permit 224.0.0.0  7.255.255.255 
              ip pim rp-candidate gigabitethernet1/0/0 group-list 10 priority 20
              access-list 20 permit 224.0.0.0  7.255.255.255
              access-list 20 permit 232.0.0.0  7.255.255.255
              ip pim rp-candidate gigabitethernet2/0/0 group-list 20 priority 10

              In this configuration the candidate RP on Ethernet interface 2 announces group address 224.0.0.0/5 and 232.0.0.0/5 which equal 224.0.0.0/4, but gives the interface the same group prefix length (5) as the candidate RP on Ethernet 1. As a result, both a Cisco router and an RFC 2362-compliant router will select the RP Ethernet interface 2.

              Example: Sparse Mode with a Single Static RP

              The following example sets the PIM RP address to 192.168.1.1 for all multicast groups and defines all groups to operate in sparse mode:

              ip multicast-routing
              interface gigiabitethernet 1/0/0
               ip pim sparse-mode
              ip pim rp-address 192.168.1.1 
              

              Note


              The same RP cannot be used for both bidirectional and sparse mode groups.


              The following example sets the PIM RP address to 172.16.1.1 for the multicast group 225.2.2.2 only:

              access list 1 225.2.2.2 0.0.0.0 
               ip pim rp-address 172.17.1.1 

              SSM with IGMPv3 Example

              The following example shows how to configure a device (running IGMPv3) for SSM:

              ip multicast-routing 
              !
              interface GigabitEthernet3/1/0 
               ip address 172.21.200.203 255.255.255.0 
               description backbone interface 
              	ip pim sparse-mode 
              ! 
              interface GigabitEthernet3/2/0 
              	ip address 131.108.1.2 255.255.255.0 
              	ip pim sparse-mode 
              	description ethernet connected to hosts 
              	ip igmp version 3 
              ! 
              ip pim ssm default 

              SSM Filtering Example

              The following example shows how to configure filtering on legacy RP routers running software releases that do not support SSM routing. This filtering will suppress all unwanted PIM-SM and MSDP traffic in the SSM range. Without this filtering, SSM will still operate, but there may be additional RPT traffic if legacy first hop and last hop routers exist in the network.

              ip access-list extended  no-ssm-range
                deny   ip any 232.0.0.0 0.255.255.255 ! SSM range
                permit ip any any
              ! Deny registering in SSM range
              ip pim accept-register list no-ssm-range
              ip access-list extended msdp-nono-list
                deny   ip any 232.0.0.0 0.255.255.255 ! SSM Range
                ! .
                ! .
                ! .
                ! See ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt for other SA
                ! messages that typically need to be filtered.
                permit ip any any
              ! Filter generated SA messages in SSM range. This configuration is only needed if there
              ! are directly connected sources to this router. The “ip pim accept-register” command
              ! filters remote sources.
              ip msdp redistribute list msdp-nono-list
              ! Filter received SA messages in SSM range. “Filtered on receipt” means messages are
              ! neither processed or forwarded. Needs to be configured for each MSDP peer.
              ip msdp sa-filter in msdp-peer1 list msdp-nono-list
              ! .
              ! .
              ! .
              ip msdp sa-filter in msdp-peerN list msdp-nono-list
              

              Bidir-PIM Example

              By default, a bidirectional RP advertises all groups as bidirectional. An access list on the RP can be used to specify a list of groups to be advertised as bidirectional. Groups with the deny keyword will operate in dense mode. A different, nonbidirectional RP address is required for groups that operate in sparse mode because a single access list only allows either a permit or deny keyword.

              The following example shows how to configure an RP for both sparse mode and bidirectional mode groups. The groups identified as 224/8 and 227/8 are bidirectional groups, and 226/8 is a sparse mode group. The RP must be configured to use different IP addresses for the sparse mode and bidirectional mode operations. Two loopback interfaces are used to allow this configuration. The addresses of these loopback interfaces must be routed throughout the PIM domain in such a way that the other routers in the PIM domain can communicate with the RP.

              ip multicast-routing
              !
              .
              .
              .
              !
              interface loopback 0 
               description One loopback address for this router’s Bidir Mode RP function
               ip address 10.0.1.1 255.255.255.0 
              ! 
              interface loopback 1 
              description One loopback address for this router’s Sparse Mode RP function 
               ip address 10.0.2.1 255.255.255.0
              !
              .
              .
              .
              !
              ip pim bidir-enable
              ip pim rp-address 10.0.1.1 45 bidir
              ip pim rp-address 10.0.2.1 46 
              !
              access-list 45 permit 224.0.0.0 0.255.255.255 
              access-list 45 permit 227.0.0.0 0.255.255.255 
              access-list 46 permit 226.0.0.0 0.255.255.255 

              Additional References

              Related Documents

              Related Topic

              Document Title

              Cisco IOS commands

              Cisco IOS Master Commands List, All Releases

              IP multicast commands

              Cisco IOS IP Multicast Command Reference

              MIBs

              MIB

              MIBs Link

              No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

              To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

              http:/​/​www.cisco.com/​go/​mibs

              Technical Assistance

              Description

              Link

              The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

              http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

              Feature Information for Configuring Basic IP Multicast in IPv4 Networks

              The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

              Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

              Table 1 Feature Information for Configuring Basic IP Multicast in IPv4 Networks

              Feature Name

              Releases

              Feature Information

              Auto RP Enhancements

              Cisco IOS XE Release 2.1

              Auto-RP automates the distribution of group-to-rendezvous point (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.

              Bidirectional PIM

              Cisco IOS XE Release 2.2

              Cisco IOS XE Release 3.8S

              Cisco IOS XE Release 3.9S

              Bidirectional PIM is an extension to the PIM suite of protocols that implements shared sparse trees with bidirectional data flow. In contrast to PIM-Sparse Mode, Bidirectional PIM avoids keeping source-specific state in a router and allows trees to scale to an arbitrary number of sources.

              In Cisco IOS XE Release 3.8S, support was added for the Cisco ISR 4400 Series Routers.

              In Cisco IOS XE Release 3.9S, support was added for the Cisco CSR 1000V.

              PIM Dense Mode Fallback Prevention in a Network Following RP Information Loss

              12.3(4)T

              12.0(28)S

              12.2(33)SRA

              12.2(33)SXH

              Cisco IOS XE Release 2.1

              15.0(1)S

              The PIM Dense Mode Fallback Prevention in a Network Following RP Information Loss feature enables you to prevent PIM-DM fallback when all RPs fail. Preventing the use of dense mode is very important to multicast networks whose reliability is critical. This feature provides a mechanism to keep the multicast groups in sparse mode, thereby preventing dense mode flooding.

              The following command was introduced by this feature: ip pim dm-fallback.

              Source Specific Multicast (SSM)

              12.3(4)T

              12.2(25)S

              12.0(28)S

              12.2(33)SXH

              12.2(33)SRA

              15.0(1)S

              Cisco IOS XE Release 2.1

              Cisco IOS XE 3.1.0SG

              Cisco IOS XE Release 3.8S

              Cisco IOS XE Release 3.9S

              SSM is an extension of IP multicast where datagram traffic is forwarded to receivers from only those multicast sources that the receivers have explicitly joined. For multicast groups configured for SSM, only source-specific multicast distribution trees (not shared trees) are created.

              In Cisco IOS XE Release 3.8S, support was added for the Cisco ISR 4400 Series Routers.

              In Cisco IOS XE Release 3.9S, support was added for the Cisco CSR 1000V.