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Bidirectional PIM

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Bidirectional PIM

Table Of Contents

Bidirectional PIM

Feature Overview

DF Election

Bidirectional Group Tree Building

Packet Forwarding

Benefits

Restrictions

Related Features and Technologies

Related Documents

Supported Platforms

Supported Standards, MIBs, and RFCs

Configuration Tasks

Configuring Bidir-PIM

Verifying Bidirectional Groups

Monitoring and Maintaining Bidir-PIM

Configuration Example

Command Reference

debug ip mpacket

debug ip pim

ip pim bidir-enable

ip pim rp-address

ip pim rp-candidate

ip pim send-rp-announce

show ip pim interface

show ip pim rp

show ip rpf


Bidirectional PIM


Feature History

Release
Modification

12.1(2)T

This feature was introduced.

12.0(18)ST

This feature was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This feature was integrated into Cisco IOS Release 12.0(22)S.


This feature module describes the Bidirectional PIM (bidir-PIM) feature. It includes the following sections:

Feature Overview

Supported Platforms

Configuration Tasks

Monitoring and Maintaining Bidir-PIM

Configuration Example

Command Reference

Feature Overview

Bidir-PIM is a variant of the Protocol Independent Multicast (PIM) suite of routing protocols for IP multicast. In PIM, packet traffic for a multicast group is routed according to the rules of the mode configured for that multicast group. The Cisco IOS implementation of PIM supports three modes for a multicast group:

Bidirectional mode

Dense mode

Sparse mode

A router can simultaneously support all three modes or any combination of them for different multicast groups. 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. Using this technique is the preferred configuration for establishing a redundant RP configuration for bidir-PIM.

Membership to a bidirectional group is signaled via 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.

Bidir-PIM is designed to be used for many-to-many applications within individual PIM domains. Multicast groups in bidirectional mode can scale to an arbitrary number of sources without incurring overhead due to the number of sources.

Bidir-PIM is derived from the mechanisms of PIM sparse mode (PIM-SM) and shares many shortest path tree (SPT) operations. Bidir-PIM also has unconditional forwarding of source traffic toward the RP upstream on the shared tree, but no registering process for sources as in PIM-SM. These modifications are necessary and sufficient to allow forwarding of traffic in all routers solely based on the (*, G) multicast routing entries. This feature eliminates any source-specific state and allows scaling capability to an arbitrary number of sources. Figure 1 and Figure 2 show the difference in state created per router for a unidirectional shared tree and source tree versus a bidirectional shared tree.

Figure 1 Unidirectional Shared Tree and Source Tree

Figure 2 Bidirectional Shared Tree

There are no fundamental differences between bidir-PIM and PIM-SM in forwarding packets downstream from the RP toward receivers. Bidir-PIM deviates substantially from PIM-SM when passing traffic from sources upstream toward the RP.

PIM-SM cannot forward traffic in the upstream direction of a tree, because it only accepts traffic from one Reverse Path Forwarding (RPF) interface. This interface (for the shared tree) points toward the RP, therefore allowing only downstream traffic flow. In this case, upstream traffic is first encapsulated into unicast register messages, which are passed from the designated router (DR) of the source toward the RP. In a second step, the RP joins an SPT that is rooted at the source. Therefore, in PIM-SM, traffic from sources traveling toward 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 the 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 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 upstream to the RP.

The DF election is based on unicast routing metrics and uses the same tie-break rules employed by PIM assert processes. 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. In addition, 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 with 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 or leave messages upstream toward the RP. When a downstream router wants to join the shared tree, the RPF neighbor in the PIM join/leave message is always the DF elected for the interface leading 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/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. In addition, an RP never joins a path back to the source, nor will it send any register stops.

Packet Forwarding

A router only creates (*, G) entries 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 (*, 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

Reduced Memory, Bandwidth, and CPU Requirements

In PIM dense mode (PIM-DM), PIM-SM, and most other multicast routing protocols such as Distance Vector Multicast Routing Protocol (DVMRP) and Multicast Open Shortest Path First (MOSPF), protocol operations and maintenance of packet forwarding state depend on signaling the presence or expiration of traffic (where "signaling" refers to both the packet forwarding engine to routing protocol process within the routers and the packet exchange part of the routing protocol). Triggering PIM assert messages, PIM register messages, and source tree forwarding state are all examples of traffic signaling.

There are several advantages to traffic signaling, but they can lead to problems for applications with a large number of sources. For example, the more sources an application has, the less frequently traffic is sent from each sender. Each time a source starts to send packets, protocol operations take place and forwarding state is established. For applications with a large number of sources, this state can time out before the source sends again, resulting in "bursty sources." Therefore, applications with a large number of sources would not only create a large amount of forwarding state (requiring memory), but they also could require high CPU usage on the Route Processor due to the accounting of frequently changing state. In addition, the signaling within the router between the Route Processor and forwarding hardware can become a bottleneck if continuously large amounts of traffic signaling must go to the Route Processor and equally large amounts of forwarding state changes must go to the forwarding engines.

Bidir-PIM solves all these problems. Not only does bidir-PIM avoid maintaining source-specific forwarding state, therefore reducing the amount of memory needed by the number of sources per multicast group, but it also does not require any traffic signaling in the protocol. Thus, bidir-PIM prevents the "bursty source" problem, saving on CPU requirements for protocol operations and avoiding potential router internal performance limits.

Easier Debugging

Because routers operating in bidirectional mode only maintain a single (*, G) entry per group, debugging multicast connectivity is made simpler than in sparse mode.

RP Tree Delivery for All Packets

In PIM-SM, the first few packets of a new source are passed encapsulated, via register packets, before the RP joins a path to the source. The need to send register packets makes PIM-SM unsuitable for applications like expanding ring searches, because the expanding ring search for those register packets will start at the RP. Bidir-PIM does not suffer from this limitation because there is no registering process.


Note For expanding ring search applications, dense mode is preferred over bidirectional mode because in dense mode every packet will travel along the SPT from the source. Therefore, the time-to-live (TTL) will more closely resemble the network neighborhood than it will when shared tree is used.


Restrictions

Partial Upgrades Not Allowed

If bidir-PIM is deployed within a domain, then it must be supported on all IP multicast-enabled routers in that domain. It is not possible to enable groups for bidir-PIM operation in a partially upgraded network.


Note Packet loops will occur immediately in networks that are only partially upgraded to support bidir-PIM.


Utilization of Network Redundancy Within Bidirectional Groups Not Allowed

A group that is in bidirectional mode has only shared tree forwarding capabilities. Shared tree and SPT forwarding cannot be mixed as in PIM-SM. Consequently, traffic for a bidirectional group will flow only along the one shared tree and can never simultaneously utilize multiple paths in a redundant network topology. Care must be taken to not overload parts of the network close to the RP, because all traffic could end up traveling through this area.

Nonbroadcast Multiaccess Mode Not Supported

Bidir-PIM does not support nonbroadcast multiaccess (NBMA) mode.

Traffic Forwarding Restrictions

Traffic in a bidirectional group will always be forwarded to the RP of that group. If no receivers are along the way to the RP, the traffic will be dropped off only at the RP. Traffic will be forwarded to the RP even if there are no receivers at all. This is a generic restriction resulting from the fact that bidir-PIM does not use traffic signaling. Without traffic signaling, the RP does not know where the currently active sources are, and therefore does not know which sources to signal traffic restrictions to.

In general, these traffic forwarding restrictions are not limitations for the applications for which bidir-PIM was intended. Different bidirectional groups can use different RPs and thus different shared trees, utilizing different parts of the network topology. For groups with many sources, the chance of having no receivers is typically small. Using the following general rules for placing the RP within a network can help avoid most of the potential shortcomings related to traffic forwarding:

In applications with a large number of active sources and a similar amount of receivers, the RP should be placed well in the middle of the network so that the bandwidth into the RP is equal to all sources and receivers and the aggregate bandwidth into the RP is optimal.

In applications where there is one or a few colocated critical stations and a large number of other stations, it is often useful to place the RP close to or directly neighboring those critical stations. This type of setup will result in the shortest possible paths between the critical stations and the other stations, resulting in both the lowest latency on these paths and best utilization of potential redundant paths. Because bidir-PIM always forwards traffic from sources toward the RP, it is often useful to place the RP close to high data rate sources. Examples of such an application is corporate education over the network, where the classroom is the critical sender station, or redundant data collector, and the multiple collectors are the crucial receivers.


Note In general, the fact that bidir-PIM forwards traffic up the shared tree toward the RP is not an advantage over PIM-SM in terms of traffic forwarding performance or typical path lengths. PIM-SM forwards the same traffic down SPTs from the sources toward the RP, and unless the unicast routing is highly asymmetric, these trees will be very similar to the RP trees. In fact, if the unicast routing is fully symmetric, then the SPTs and RP trees will be identical. The difference is only in the forwarding state, which in PIM-SM is per source and therefore does not scale to the dimensions of bidir-PIM.

The fact that PIM-SM keeps per-source state for source-to-RP forwarding also allows it to effectively restrict traffic toward the RP. In PIM-SM, if there are no receivers to a multicast group, then traffic will not flow toward the RP. The RP will stop the registering from the DR of the source and will not join the SPT to the source. If there are receivers only on branches of the network between the source and the RP in PIM-SM, traffic will also flow only toward the RP up to that branching point, but not further on toward the RP. This latter feature is an improvement beyond the PIM-SM version 2 protocol, and is only implemented in Cisco IOS Release 12.0 and later releases.


Related Features and Technologies

The bidir-PIM feature is an extension of the existing PIM-SM feature, which is documented in the "Configuring IP Multicast" chapter of the Cisco IOS IP Routing Configuration Guide, Release 12.2 and the "IP Multicast Routing Commands" chapter of the Cisco IOS IP Command Reference, Volume 3 of 3: Multicast, Release 12.2.

Related Documents

For related information on this feature, refer to the following documents:

Cisco IOS IP Configuration Guide, Release 12.2

Cisco IOS IP Command Reference, Volume 3 of 3: Multicast, Release 12.2

The bidir-PIM feature in Cisco IOS Release 12.1(2)T and 12.0(18)ST is based on the following Internet Engineering Task Force (IETF) protocol specification:

draft-ietf-pim-bidir-03.txt

Supported Platforms

Bidir-PIM is supported on all platforms for which IP multicast in Cisco IOS Release 12.1(2)T, 12.0(18)ST, and later releases is supported, except for the Cisco 12000 series Internet routers.

Bidir-PIM is also supported in the process switching and in the fast-switching path. In addition, it is supported on the Cisco 7500 series routers in the multicast distributed fast-switching path.

Determining Platform Support Through Cisco Feature Navigator

Cisco IOS software is packaged in feature sets that are supported on specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.

Cisco Feature Navigator is a web-based tool that enables you to quickly determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.

To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions found at this URL:

http://www.cisco.com/register

Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:

http://www.cisco.com/go/fn

Availability of Cisco IOS Software Images

Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.

Supported Standards, MIBs, and RFCs

Standards

No new or modified standards are supported by this feature.

MIBs

No new or modified MIBs are supported by this feature.

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

http://tools.cisco.com/ITDIT/MIBS/servlet/index

If Cisco MIB Locator does not support the MIB information that you need, you can also obtain a list of supported MIBs and download MIBs from the Cisco MIBs page at the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

To access Cisco MIB Locator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions found at this URL:

http://www.cisco.com/register

RFCs

No new or modified RFCs are supported by this feature.

Configuration Tasks

See the following sections for configuration tasks for the bidir-PIM feature. Each task in the list is identified as either required or optional:

Configuring Bidir-PIM (required)

Verifying Bidirectional Groups (optional)

Configuring Bidir-PIM

Most of the configuration requirements for bidir-PIM are the same as those for configuring PIM-SM. When bidir-PIM is enabled on a router, configure the multicast groups that you want to operate in bidirectional mode. Similar to PIM-SM, this configuration can be done via Auto-RP, static RP configurations, or the PIM Version 2 bootstrap router (PIMv2 BSR) mechanism.

To enable bidir-PIM, use the following command in global configuration mode:

Command
Purpose

Router(config)# ip pim bidir-enable

Enables bidir-PIM on a router.


To configure which multicast groups you want to operate in bidirectional mode, use one of the following commands in global configuration mode, depending on which method you use to distribute group-to-RP mappings:

Command
Purpose

Router(config)# ip pim rp-address ip-address [access-list] [override] bidir

Configures the address of a PIM RP for a particular group, and specifies bidirectional mode. Use this command when you are not distributing group-to-RP mappings using either Auto-RP or the PIMv2 BSR mechanism.

Router(config)#  ip pim rp-candidate type-number [group-list access-list] bidir

Configures the router to advertise itself as a PIMv2 candidate RP to the BSR, and specifies bidirectional mode. Use this command when you are using the PIMv2 BSR mechanism to distribute group-to-RP mappings.

Router(config)# ip pim send-rp-announce type-number scope ttl [group-list access-list] [interval seconds] bidir

Configures the router to use Auto-RP to configure the groups for which the router is willing to act as RP, and specifies bidirectional mode. Use this command when you are using Auto-RP to distribute group-to-RP mappings.


Verifying Bidirectional Groups

To verify configuration of bidirectional groups, use the following show commands:

To examine RP-to-group mappings and determine the bidirectional groups advertised by an RP, use the show ip pim rp mapping command in EXEC mode.

To display the IP multicast routing table information for groups operating in bidirectional mode, sparse mode, and dense mode, use the show ip mroute command in EXEC mode.

To display information about the elected DF for each RP of an interface and the metric associated with the DF, use the show ip pim interface df command in EXEC mode.

Monitoring and Maintaining Bidir-PIM

Command
Purpose

Router# show ip pim interface [type number] [df | count] [rp-address]

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

Router# show ip pim rp [mapping | metric] [rp-address]

Displays information about configured RPs, learned via Auto-RP or BSR, along with their unicast routing metric.


Configuration 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. 224/8 and 227/8 are bidirectional groups, 226/8 is sparse mode, and 225/8 is dense mode. 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 such that the other routers in the PIM domain can receive Auto-RP announcements and communicate with the RP.

ip multicast-routing !Enable IP multicast routing
ip pim bidir-enable  !Enable bidir-PIM
!
interface loopback 0
 description One Loopback adddress for this routers Bidir Mode RP function
 ip address 10.0.1.1 255.255.255.0
 ip pim sparse-dense-mode
!
interface loopback 1
 description One Loopback adddress for this routers Sparse Mode RP function
 ip address 10.0.2.1 255.255.255.0
 ip pim sparse-dense-mode

ip pim send-rp-announce Loopback0 scope 10 group-list 45 bidir
ip pim send-rp-announce Loopback1 scope 10 group-list 46
ip pim send-rp-discovery scope 10

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 45 deny   225.0.0.0 0.255.255.255

access-list 46 permit 226.0.0.0 0.255.255.255

Command Reference

This section documents the following modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.

debug ip mpacket

debug ip pim

ip pim bidir-enable

ip pim rp-address

ip pim rp-candidate

ip pim send-rp-announce

show ip pim interface

show ip pim rp

show ip rpf

debug ip mpacket

To display IP multicast packets received and sent, use the debug ip mpacket privileged EXEC command. To disable the debugging output, use the no form of this command.

debug ip mpacket [detail | fastswitch] [access-list] [group]

no debug ip mpacket [detail | fastswitch] [access-list] [group]

Syntax Description

detail

(Optional) Causes the debug ip mpacket command to display IP header information and MAC address information.

fastswitch

(Optional) Displays IP packet information in the fast path.

access-list

(Optional) Access list number.

group

(Optional) Group name or address.


Defaults

Displays all IP multicast packets switched at the process level.

Command Modes

Privileged EXEC

Command History

Release
Modification

10.2

This command was introduced.

12.1(2)T

The fastswitch keyword was added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

This command displays information for multicast IP packets that are forwarded from this router. By using the access-list or group argument, you can limit the display to multicast packets from sources described by the access list or a specific multicast group.

Use this command with the debug ip packet command to display additional packet information.


Note The debug ip mpacket command generates many messages. Use this command with care so that performance on the network is not affected by the debug message traffic.


Examples

The following is sample output from the debug ip mpacket command:

Router# debug ip mpacket 224.2.0.1 

IP: s=10.188.34.54 (Ethernet1), d=224.2.0.1 (Tunnel0), len 88, mforward 
IP: s=10.188.34.54 (Ethernet1), d=224.2.0.1 (Tunnel0), len 88, mforward 
IP: s=10.188.34.54 (Ethernet1), d=224.2.0.1 (Tunnel0), len 88, mforward 
IP: s=10.162.3.27 (Ethernet1), d=224.2.0.1 (Tunnel0), len 68, mforward 

Table 1 describes the significant fields shown in the display.

Table 1 debug ip mpacket Field Descriptions 

Field
Description

IP

IP packet.

s=

Source address of the packet.

(Ethernet1)

Name of the interface that received the packet.

d=

Multicast group address that is the destination for this packet.

(Tunnel0)

Outgoing interface for the packet.

len 88

Number of bytes in the packet. This value will vary depending on the application and the media.

mforward

Packet has been forwarded.


Related Commands

Command
Description

debug ip dvmrp

Displays information on DVMRP packets received and sent.

debug ip igmp

Displays information on IGMP packets received and sent, and IGMP host-related events.

debug ip mrm

Displays MRM control packet activity.

debug ip packet

Displays general IP debugging information and IPSO security transactions.

debug ip sd

Displays all SD announcements received.


debug ip pim

To display information on Protocol Independent Multicast (PIM) packets received and sent, and to display PIM-related events, use the debug ip pim privileged EXEC command. To disable the debugging output, use the no form of this command.

debug ip pim [group | df [rp-address]]

no debug ip pim [group | df [rp-address]]

Syntax Description

group

(Optional) Group name or address to monitor the packet activity of a single group.

df

(Optional) When bidirectional PIM is used, displays all designated forwarder (DF) election messages.

rp-address

(Optional) Rendezvous point (RP) IP address.


Defaults

Displays all PIM packets.

Command Modes

Privileged EXEC

Command History

Release
Modification

10.2

This command was introduced.

12.1(2)T

The df keyword was added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

PIM uses Internet Group Management Protocol (IGMP) packets to communicate between routers and advertise reachability information.

Use this command with the debug ip igmp and debug ip mrouting commands to display additional multicast routing information.

Examples

The following is sample output from the debug ip pim command:

Router# debug ip pim 224.2.0.1 

PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Received Join/Prune on Tunnel0 from 10.3.84.1 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33
PIM: Received RP-Reachable on Ethernet1 from 172.16.20.31 
PIM: Update RP expiration timer for 224.2.0.1 
PIM: Forward RP-reachability packet for 224.2.0.1 on Tunnel0 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Prune-list (10.221.196.51/32, 224.2.0.1)   
PIM: Set join delay timer to 2 seconds for (10.221.0.0/16, 224.2.0.1) on Ethernet1 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.6 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Received Join/Prune on Tunnel0 from 10.3.84.1 
PIM: Join-list: (*, 224.2.0.1) RP 172.16.20.31 
PIM: Add Tunnel0 to (*, 224.2.0.1), Forward state 
PIM: Join-list: (10.0.0.0/8, 224.2.0.1)   
PIM: Add Tunnel0 to (10.0.0.0/8, 224.2.0.1), Forward state 
PIM: Join-list: (10.4.0.0/16, 224.2.0.1)   
PIM: Prune-list (172.24.84.16/28, 224.2.0.1) RP-bit set RP 172.24.84.16 
PIM: Send Prune on Ethernet1 to 172.24.37.6 for (172.24.84.16/28, 224.2.0.1), RP 
PIM: For RP, Prune-list: 10.9.0.0/16 
PIM: For RP, Prune-list: 10.16.0.0/16 
PIM: For RP, Prune-list: 10.49.0.0/16 
PIM: For RP, Prune-list: 10.84.0.0/16 
PIM: For RP, Prune-list: 10.146.0.0/16 
PIM: For 10.3.84.1, Join-list: 172.24.84.16/28 
PIM: Send periodic Join/Prune to RP via 172.24.37.6 (Ethernet1) 

The following lines appear periodically when PIM is running in sparse mode and indicate to this router the multicast groups and multicast sources in which other routers are interested:

PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 
PIM: Received Join/Prune on Ethernet1 from 172.24.37.33 

The following lines appear when an RP message is received and the RP timer is reset. The expiration timer sets a checkpoint to make sure the RP still exists; otherwise a new RP must be discovered.

PIM: Received RP-Reachable on Ethernet1 from 172.16.20.31 
PIM: Update RP expiration timer for 224.2.0.1 
PIM: Forward RP-reachability packet for 224.2.0.1 on Tunnel0 

The prune message in the following line states that this router is not interested in the source address information. This message tells an upstream router to stop forwarding multicast packets from this source.

PIM: Prune-list (10.221.196.51/32, 224.2.0.1)   

In the following line, a second router on the network wants to override the prune message that the upstream router just received. The timer is set at a random value so that if additional routers on the network still want to receive multicast packets for the group, only one will actually send the message. The other routers will receive the join message and then suppress sending their own message.

PIM: Set join delay timer to 2 seconds for (10.221.0.0/16, 224.2.0.1) on Ethernet1 

In the following line, a join message is sent toward the RP for all sources:

PIM: Join-list: (*, 224.2.0.1) RP 172.16.20.31 

In the following lines, the interface is being added to the outgoing interface (OIF) of the (*, G) and (S, G) mroute table entry so that packets from the source will be forwarded out that particular interface:

PIM: Add Tunnel0 to (*, 224.2.0.1), Forward state 
PIM: Add Tunnel0 to (10.0.0.0/8, 224.2.0.1), Forward state 

The following line appears in sparse mode only. There are two trees on which data may be received: the RP tree and the source tree. In dense mode there is no RP. After the source and the receiver have discovered one another at the RP, the first hop router for the receiver will usually join to the source tree rather than the RP tree.

PIM: Prune-list (172.24.84.16/28, 224.2.0.1) RP-bit set RP 172.24.84.16 

The Send Prune message in the next line shows that a router is sending a message to a second router stating that the first router no longer wants to receive multicast packets for the (S, G). The "RP" term toward the end of the message indicates that the router is pruning the RP tree and is most likely joining the source tree, although the router may not have downstream members for the group or downstream routers with members of the group. The output shows the specific sources from which this router no longer wants to receive multicast packets.

PIM: Send Prune on Ethernet1 to 172.24.37.6 for (172.24.84.16/28, 224.2.0.1), RP 

The following lines indicate that a prune message is sent toward the RP so that the router can join the source tree rather than the RP tree:

PIM: For RP, Prune-list: 10.9.0.0/16 
PIM: For RP, Prune-list: 10.16.0.0/16 
PIM: For RP, Prune-list: 10.49.0.0/16 

In the following line, a periodic message is sent toward the RP. The default period is once per minute. prune and join messages are sent toward the RP or source rather than directly to the RP or source. It is the responsibility of the next hop router to take proper action with this message, such as continuing to forward it to the next router in the tree.

PIM: Send periodic Join/Prune to RP via 172.24.37.6 (Ethernet1)

Related Commands

Command
Description

debug ip dvmrp

Displays information on DVMRP packets received and sent.

debug ip igmp

Displays information on IGMP packets received and sent, and displays IGMP host-related events.

debug ip igrp transactions

Displays transaction information on IGRP routing transactions.

debug ip mrouting

Displays changes to the IP multicast routing table.

debug ip sd

Displays all SD announcements received.


ip pim bidir-enable

To enable Bidirectional Protocol Independent Multicast (bidir-PIM), use the ip pim bidir-enable global configuration command. To disable bidir-PIM, use the no form of this command.

ip pim bidir-enable

no ip pim bidir-enable

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

12.0(18)ST

This command was introduced.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

Bidir-PIM is disabled by default to ensure complete backward compatibility when upgrading a router to Cisco IOS Release 12.0(18)ST or a later release.

When bidir-PIM is disabled, the router will behave similarly to a router without bidir-PIM support. The following conditions will apply:

PIM hello messages sent by the router will not contain the bidirectional mode option.

The router will not send designated forwarder (DF) election messages and will ignore DF election messages it receives.

The ip pim rp-address, ip pim send-rp-announce, and ip pim rp-candidate global configuration commands will be treated as follows:

If these commands are configured when bidir-PIM is disabled, bidirectional mode will not be a configuration option.

If these commands are configured with the bidirectional mode option when bidir-PIM is enabled and then bidir-PIM is disabled, these commands will be removed from the command-line interface (CLI). In this situation, these commands must be configured again with the bidirectional mode option when bidir-PIM is reenabled.

The df keyword for the show ip pim interface EXEC configuration command and debug ip pim privileged EXEC configuration command is not supported.

Examples

The following example shows how to configure a rendezvous point (RP) for both sparse mode and bidirectional mode groups. 224/8 and 227/8 are bidirectional groups, 226/8 is sparse mode, and 225/8 is dense mode. 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 such that the other routers in the PIM domain can receive Auto-RP announcements and communicate with the RP.

ip multicast-routing !Enable IP multicast routing
ip pim bidir-enable  !Enable bidir-PIM
!
interface loopback 0
 description One Loopback adddress for this routers Bidir Mode RP function
 ip address 10.0.1.1 255.255.255.0
 ip pim sparse-dense-mode
!
interface loopback 1
 description One Loopback adddress for this routers Sparse Mode RP function
 ip address 10.0.2.1 255.255.255.0
 ip pim sparse-dense-mode

ip pim send-rp-announce Loopback0 scope 10 group-list 45 bidir
ip pim send-rp-announce Loopback1 scope 10 group-list 46
ip pim send-rp-discovery scope 10

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 45 deny   225.0.0.0 0.255.255.255

access-list 46 permit 226.0.0.0 0.255.255.255

Related Commands

Command
Description

ip pim rp-address

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

ip pim rp-candidate

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

ip pim send-rp-announce

Uses Auto-RP to configure for which groups the router is willing to act as RP.


ip pim rp-address

To configure the address of a Protocol Independent Multicast (PIM) rendezvous point (RP) for a particular group, use the ip pim rp-address global configuration command. To remove an RP address, use the no form of this command.

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

no ip pim rp-address

Syntax Description

ip-address

IP address of a router to be a PIM RP. This is a unicast IP address in four-part, dotted notation.

access-list

(Optional) Number or name of an access list that defines for which multicast groups the RP should be used.

override

(Optional) Indicates that if there is a conflict, the RP configured with this command prevails over the RP learned by Auto-RP.

bidir

(Optional) Indicates that the multicast groups specified by the access-list argument are to operate in bidirectional mode. If the command is configured without this option, the groups specified will operate in PIM sparse mode.


Defaults

No PIM RPs are preconfigured.

Command Modes

Global configuration

Command History

Release
Modification

10.2

This command was introduced.

11.1

The override keyword was added.

12.1(2)T

The bidir keyword was added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

In the Cisco IOS implementation of PIM, each multicast group individually operates in one of the following modes: dense mode, sparse mode, or bidirectional mode. In addition to the mode, groups in sparse mode or bidirectional mode need to have the IP address of one router to operate as the RP for the group. All routers in a PIM domain need to have a consistent configuration for the mode and RP addresses of the multicast groups.

The Cisco IOS software learns the mode and RP addresses of multicast groups via the following three mechanisms: static configuration, Auto-RP, and bootstrap router (BSR). Use the ip pim rp-address command to statically define the mode of operations and RP address for multicast groups that are to operate in sparse mode or bidirectional mode. By default, groups will operate in dense mode. There are no commands to explicitly define groups to operate in dense mode.

You can configure the Cisco IOS software to use a single RP for more than one group. The conditions specified by the access list determine for which groups the RP can be used. If no access list is configured, the RP is used for all groups. A PIM router can use multiple RPs, but only one per group.

If multiple ip pim rp-address commands are configured, the following rules apply to a multicast group:

Longest prefix match selection on access lists: If a group is matched by the access list of more than one ip pim rp-address command, then the mode and RP for the group are determined by the ip pim rp-address command with the longest prefix mask. An ip pim rp-address command with no access list parameter behaves like the same command with an access list that matches all IP addresses and will always have the shorter prefix length in comparison.

Highest RP IP address selection: If a group is matched by the access list of more than one ip pim rp-address command whose prefix masks are all the same lengths, then the mode and RP for the group are determined by the ip pim rp-address command with the highest RP address parameter.

Static evaluation: The mode and RP selection for a group are static and do not depend on the reachability of the individual RPs. The router will not start using an RP with a lower IP address or a shorter prefix length match if the better RP is not reachable. Use Auto-RP, BSR, or Anycast-RP to configure redundancy.

One IP address per command: An IP address can be used as a parameter for only one ip pim rp-address command. If an ip pim rp-address command is configured with an IP address parameter that was previously used to configure an older ip pim rp-address command, then this old command will be replaced with the newly configured command. This restriction also means that only one IP address can be used to provide RP functions for either sparse mode or bidirectional mode groups. Use different IP addresses of the same router to provide RP functions for both sparse mode and bidirectional mode from the same router.

One access list per command: A specific access list can be used as a parameter for only one ip pim rp-address command. If an ip pim rp-address command is configured with an access list parameter that was previously used to configure an older ip pim rp-address command, then this old command will be replaced with the newly configured command.

Static definitions for the group mode and RP address of the ip pim rp-address command may be used together with dynamically learned group mode and RP address mapping through Auto-RP or BSR. The following rules apply to a multicast group:

Group mode and RP address mappings learned through Auto-RP and BSR take precedence over mappings statistically defined by the ip pim rp-address command without the override keyword. Commands with the override keyword take precedence over dynamically learned mappings.

If you are using Auto-RP to distribute group-to-RP mappings, use the bidir keyword with the ip pim send-rp-announce global configuration command.

If you are using the PIM Version 2 BSR mechanism to distribute group-to-RP mappings, use the bidir keyword with the ip pim rp-candidate global configuration command.

Examples

The following example sets the PIM RP address to 198.92.37.33 for all multicast groups and defines all groups to operate in sparse mode:

ip pim rp-address 198.92.37.33

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


The following example sets the PIM RP address to 147.106.6.22 for the multicast group 225.2.2.2 only:

access list 1 permit 225.2.2.2 0.0.0.0
 ip pim rp-address 147.106.6.22 1

Related Commands

Command
Description

access-list (IP standard)

Defines a standard IP access list.

ip pim send-rp-announce

Uses Auto-RP to configure for which groups the router is willing to act as RP.

ip pim rp-candidate

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


ip pim rp-candidate

To configure the router to advertise itself as a Protocol Independent Multicast (PIM) Version 2 candidate rendezvous point (RP) to the bootstrap router (BSR), use the ip pim rp-candidate global configuration command. To remove this router as a candidate for being an RP, use the no form of this command.

ip pim rp-candidate type-number [group-list access-list] [bidir]

no ip pim rp-candidate

Syntax Description

type-number

IP address associated with this interface type and number on this router is advertised as a candidate RP address.

group-list access-list

(Optional) Standard IP access list number or name that defines the group prefixes that are advertised in association with the RP address. The access list name cannot contain a space or quotation mark, and must begin with an alphabetic character to avoid ambiguity with numbered access lists.

bidir

(Optional) Indicates that the multicast groups specified by the access-list argument are to operate in bidirectional mode. If the command is configured without this option, the groups specified will operate in PIM sparse mode.


Defaults

Disabled

Command Modes

Global configuration

Command History

Release
Modification

11.3 T

This command was introduced.

12.1(2)T

The bidir keyword was added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

This command causes the router to send a PIM Version 2 message advertising itself as a candidate RP to the BSR. The addresses allowed by the access list, together with the router identified by the type and number, constitute the RP and its range of addresses for which it is responsible.

Use this command only in backbone routers that have good connectivity to all parts of the PIM domain. That is, a stub router that relies on an on-demand dialup link to connect to the rest of the PIM domain is not a good candidate RP.

Use this command with the bidir keyword when you want bidirectional forwarding and you are using the PIM Version 2 BSR mechanism to distribute group-to-RP mappings. Other options are as follows:

If you are using Auto-RP to distribute group-to-RP mappings, use the bidir keyword with the ip pim send-rp-announce global configuration command.

If you are not distributing group-to-RP mappings using either Auto-RP or the PIM Version 2 Bootstrap mechanism, use the bidir keyword with the ip pim rp-address global configuration command.

Examples

The following example configures the router to advertise itself as a candidate RP to the BSR in its PIM domain. Standard access list number 4 specifies the group prefix associated with the RP that has the address identified by Ethernet interface 2. That RP is responsible for the groups with the prefix 239.

ip pim rp-candidate 198.92.37.33 ethernet 2 group-list 4
access-list 4 permit 239.0.0.0 0.255.255.255

Related Commands

Command
Description

ip pim bsr-candidate

Configures the router to announce its candidacy as a BSR.

ip pim rp-address

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

ip pim rp-announce-filter

Filters incoming Auto-RP announcement messages sent from the RP.

ip pim send-rp-announce

Uses Auto-RP to configure for which groups the router is willing to act as RP.


ip pim send-rp-announce

To use Auto-RP to configure groups for which the router will act as a rendezvous point (RP), use the ip pim send-rp-announce global configuration command. To unconfigure this router as an RP, use the no form of this command.

ip pim send-rp-announce type-number scope ttl [group-list access-list] [interval seconds] [bidir]

no ip pim send-rp-announce

Syntax Description

type-number

Interface type and number that identify the RP address.

scope ttl

Time-to-live (TTL) value that limits the number of Auto-RP announcements.

group-list access-list

(Optional) Standard IP access list number or name that defines the group prefixes that are advertised in association with the RP address. The access list name cannot contain a space or quotation mark, and must begin with an alphabetic character to avoid ambiguity with numbered access lists.

interval seconds

(Optional) Specifies the interval between RP announcements( in seconds). The total hold time of the RP announcements is automatically set to three times the value of the interval. The default interval is 60 seconds.

bidir

(Optional) Indicates that the multicast groups specified by the access-list argument are to operate in bidirectional mode. If the command is configured without this option, the groups specified will operate in Protocol Independent Multicast sparse mode (PIM-SM).


Defaults

Auto-RP is disabled.

Command Modes

Global configuration

Command History

Release
Modification

11.1

This command was introduced.

12.1(2)T

The following keywords and argument were added:

interval seconds

bidir

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

Use this command in the router you want to serve as the RP. When you are using Auto-RP to distribute group-to-RP mappings, this command causes the router to send an Auto-RP announcement message to the well-known group CISCO-RP-ANNOUNCE (224.0.1.39). This message announces the router as a candidate RP for the groups in the range described by the access list.

Use this command with the bidir keyword when you want bidirectional forwarding, and you are using Auto-RP to distribute group-to-RP mappings. Other options are as follows:

If you are using the PIM Version 2 Bootstrap mechanism to distribute group-to-RP mappings, use the bidir keyword with the ip pim rp-candidate global configuration command.

If you are not distributing group-to-RP mappings using either Auto-RP or the PIM Version 2 Bootstrap mechanism, use the bidir keyword with the ip pim rp-address global configuration command.

Examples

The following example sends RP announcements out all PIM-enabled interfaces for a maximum of 31 hops. The IP address by which the router wants to be identified as RP is the IP address associated with Ethernet interface 0. Access list 5 describes the groups for which this router serves as RP.

ip pim send-rp-announce ethernet0 scope 31 group-list 5
access-list 5 permit 224.0.0.0 15.255.255.255

Related Commands

Command
Description

access-list (IP standard)

Defines a standard IP access list.

ip pim rp-candidate

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

ip pim rp-address

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


show ip pim interface

To display information about interfaces configured for Protocol Independent Multicast (PIM), use the show ip pim interface EXEC command.

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

Syntax Description

type number

(Optional) Interface type and number.

df

(Optional) When bidirectional PIM is used, displays the IP address of the elected designated forwarder (DF) for each rendezvous point (RP) of an interface.

count

(Optional) Number of packets received and sent out the interface.

rp-address

(Optional) RP IP address.


Defaults

If no interface is specified, all interfaces are displayed.

Command Modes

EXEC

Command History

Release
Modification

10.0

This command was introduced.

12.1(2)T

The df keyword and rp-address argument were added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

This command works only on interfaces that are configured for PIM.

Examples

The following is sample output from the show ip pim interface command:

Router# show ip pim interface

Address          Interface          Mode    Neighbor  Query     DR
                                            Count     Interval
198.92.37.6      Ethernet0          Dense   2         30        198.92.37.33
198.92.36.129    Ethernet1          Dense   2         30        198.92.36.131
10.1.37.2        Tunnel0            Dense   1         30        0.0.0.0

The following is sample output from the show ip pim interface command when the count keyword is specified:

Router# show ip pim interface count

Address          Interface          FS  Mpackets In/Out
171.69.121.35    Ethernet0          *   548305239/13744856
171.69.121.35    Serial0.33         *   8256/67052912
198.92.12.73     Serial0.1719       *   219444/862191

The following are sample outputs from the show ip pim interface command when the df keyword is specified:

Router# show ip pim interface df

Interface          RP               DF Winner        Metric          Uptime
Ethernet3/3        10.10.0.2        10.4.0.2         0               00:03:49
                   10.10.0.3        10.4.0.3         0               00:01:49
                   10.10.0.5        10.4.0.4         409600          00:01:49
Ethernet3/4        10.10.0.2        10.5.0.2         0               00:03:49
                   10.10.0.3        10.5.0.2         409600          00:02:32
                   10.10.0.5        10.5.0.2         435200          00:02:16
Loopback0          10.10.0.2        10.10.0.2        0               00:03:49
                   10.10.0.3        10.10.0.2        409600          00:02:32
                   10.10.0.5        10.10.0.2        435200          00:02:16

Router# show ip pim interface Ethernet3/3 df 10.10.0.3

Designated Forwarder election for Ethernet3/3, 10.4.0.2, RP 10.10.0.3
  State                           Non-DF
  Offer count is                  0
  Current DF ip address           10.4.0.3
  DF winner up time               00:02:33
  Last winner metric preference   0
  Last winner metric              0


Table 2 describes the significant fields shown in the displays.

Table 2 show ip pim interface Field Descriptions 

Field
Description

Address

Interface IP address of the router.

Interface

Interface type and number that is configured to run PIM.

Mode

Multicast mode in which the Cisco IOS software is operating. This can be dense mode or sparse mode. DVMRP indicates that a Distance Vector Multicast Routing Protocol tunnel is configured.

Neighbor Count

Number of PIM neighbors that have been discovered through this interface. If the Neighbor Count is 1 for a DVMRP tunnel, the neighbor is active (receiving probes and reports).

Query Interval

Frequency (in seconds) of PIM router-query messages, as set by the ip pim query-interval interface configuration command. The default is 30 seconds.

DR

IP address of the designated router on a network. Note that serial lines do not have designated routers, so the IP address is shown as 0.0.0.0.

FS

An asterisk (*) in this column indicates that fast switching is enabled.

Mpackets In/Out

Number of packets into and out of the interface since the box has been up.

RP

IP address of the RP.

DF Winner

IP address of the elected DF.

Metric

Unicast routing metric to the RP announced by the DF.

Uptime

Length of time the RP has been up (in days and hours). If less than 1 day, time is expressed in hours:minutes:seconds.

State

Indicates whether the specified interface is an elected DF.

Offer count is

Number of PIM DF election offer messages that the router has sent out the interface during the current election interval.

Current DF ip address

IP address of the current DF.

DF winner up time

Length of time the current DF has been up (in days and hours). If less than 1 day, time is expressed in hours:minutes:seconds.

Last winner metric preference

The preference value used for selecting the unicast routing metric to the RP announced by the DF.

Last winner metric

Unicast routing metric to the RP announced by the DF.


Related Commands

Command
Description

ip pim

Enables PIM on an interface.

show ip pim neighbor

Lists the PIM neighbors discovered by the Cisco IOS software.


show ip pim rp

To display active rendezvous points (RPs) that are cached with associated multicast routing entries, use the show ip pim rp EXEC command.

show ip pim rp [mapping | metric] [rp-address]

Syntax Description

mapping

(Optional) Displays all group-to-RP mappings of which the router is aware (either configured or learned from Auto-RP).

metric

(Optional) Displays the unicast routing metric to the RPs configured statically or learned via Auto-RP or bootstrap router (BSR).

rp-address

(Optional) RP IP address.


Defaults

If no RP is specified, all active RPs are displayed.

Command Modes

EXEC

Command History

Release
Modification

10.2

This command was introduced.

12.1(2)T

The metric keyword and rp-address argument were added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Examples

The following is sample output of the show ip pim rp command:

Router# show ip pim rp

Group:227.7.7.7, RP:10.10.0.2, v2, v1, next RP-reachable in 00:00:48

The following is sample output of the show ip pim rp command when the mapping keyword is specified:

Router# show ip pim rp mapping

PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent

Group(s) 227.0.0.0/8
  RP 10.10.0.2 (?), v2v1, bidir
    Info source:10.10.0.2 (?), via Auto-RP
         Uptime:00:01:42, expires:00:00:32
Group(s) 228.0.0.0/8
  RP 10.10.0.3 (?), v2v1, bidir
    Info source:10.10.0.3 (?), via Auto-RP
         Uptime:00:01:26, expires:00:00:34
Group(s) 229.0.0.0/8
  RP 10.10.0.5 (mcast1.cisco.com), v2v1, bidir
    Info source:10.10.0.5 (mcast1.cisco.com), via Auto-RP
         Uptime:00:00:52, expires:00:00:37
Group(s) (-)230.0.0.0/8
  RP 10.10.0.5 (mcast1.cisco.com), v2v1, bidir
    Info source:10.10.0.5 (mcast1.cisco.com), via Auto-RP
         Uptime:00:00:52, expires:00:00:37


The following is sample output of the show ip pim rp command when the metric keyword is specified:

Router# show ip pim rp metric

RP Address      Metric Pref    Metric       Flags   RPF Type   Interface
10.10.0.2       0              0              L     unicast    Loopback0
10.10.0.3       90             409600         L     unicast    Ethernet3/3
10.10.0.5       90             435200         L     unicast    Ethernet3/3


Table 3 describes the significant fields shown in the displays.

Table 3 show ip pim rp Field Descriptions 

Field
Description

Group

Address of the multicast group about which to display RP information.

RP

Address of the RP for that group.

v2

Indicates that the RP is running Protocol Independent Multicast (PIM) Version 2.

v1

Indicates that the RP is running PIM Version 1.

next RP-reachable in...

Indicates the time the next RP-reachable message will be sent. Time is expressed in hours:minutes:seconds.

bidir

Indicates that the RP is operating in bidirectional mode.

Info source

RP mapping agent that advertised the mapping.

(?)

Indicates that no Domain Name System (DNS) has been specified.

via Auto-RP

Indicates that RP was learned via Auto-RP.

Uptime

Length of time the RP has been up (in days and hours). If less than 1 day, time is expressed in hours:minutes:seconds.

expires

Time in hours:minutes:seconds in which the entry will expire.

Metric Pref

The preference value used for selecting the unicast routing metric to the RP announced by the designated forwarder (DF).

Metric

Unicast routing metric to the RP announced by the DF.

Flags

Indicates the flags set for the specified RP. The following are descriptions of possible flags:

C—RP is configured.

L—RP learned via Auto-RP or BSR.

RPF Type

Routing table from which this route was obtained, either unicast, Distance Vector Multicast Routing Protocol (DVMRP), or static mroute.

Interface

Interface type and number that is configured to run PIM.


show ip rpf

To display how IP multicast routing does Reverse Path Forwarding (RPF), use the show ip rpf EXEC command.

show ip rpf {source-address | source-name} [metric]

Syntax Description

source-address | source-name

Displays the RPF information for the specified source address or name.

metric

(Optional) Displays the unicast routing metric.


Defaults

If no source is specified, all sources are displayed.

Command Modes

EXEC

Command History

Release
Modification

11.0

This command was introduced.

12.1(2)T

The metric keyword was added.

12.0(18)ST

This command was integrated into Cisco IOS Release 12.0(18)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.


Usage Guidelines

The router can reverse path forward from multiple routing tables (that is, the unicast routing table, Distance Vector Multicast Routing Protocol (DVMRP) routing table, or static mroutes). This command tells you from where the information is retrieved.

Examples

The following is sample output of the show ip rpf command:

Router# show ip rpf 171.69.10.13

RPF information for sj-eng-mbone.cisco.com (171.69.10.13)
  RPF interface: BRI0
  RPF neighbor: eng-isdn-pri3.cisco.com (171.69.121.10)
  RPF route/mask: 171.69.0.0/255.255.0.0
  RPF type: unicast
  RPF recursion count: 0
  Doing distance-preferred lookups across tables

The following is sample output of the show ip rpf command when the metric command is specified:

Router# show ip rpf 171.69.10.13 metric

RPF information for sj-eng-mbone.cisco.com (171.69.10.13)
  RPF interface: BRI0
  RPF neighbor: eng-isdn-pri3.cisco.com (171.69.121.10)
  RPF route/mask: 171.69.0.0/255.255.0.0
  RPF type: unicast
  RPF recursion count: 0
  Doing distance-preferred lookups across tables
  Metric preference: 110
  Metric: 11

Table 4 describes the significant fields shown in the displays.

Table 4 show ip rpf Field Descriptions

Field
Description

RPF information for sj-eng-mbone.cisco.com (171.69.10.13)

Host name and address that this information concerns.

RPF interface

For the given source, interface from which the router expects to get packets.

RPF neighbor

For the given source, neighbor from which the router expects to get packets.

RPF route/mask

Route number and mask that matched against this source.

RPF type

Routing table from which this route was obtained, either unicast, DVMRP, or static mroute.

RPF recursion count

Indicates the number of times the route is recursively resolved.

Doing distance-preferred...

Indicates whether RPF was determined based on distance or length of mask.

Metric preference

The preference value used for selecting the unicast routing metric to the RP announced by the designated forwarder (DF).

Metric

Unicast routing metric to the RP announced by the DF.