[an error occurred while processing this directive]

Networking Software (IOS & NX-OS)

PIM Dense Mode State Refresh

Hierarchical Navigation

Downloads

 Feedback

Table Of Contents

PIM Dense Mode State Refresh

Feature Overview

Benefits

Restrictions

Related Features and Technologies

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Verifying PIM Dense Mode State Refresh Configuration

Monitoring and Maintaining PIM DM State Refresh

Configuration Examples

Command Reference


PIM Dense Mode State Refresh

This feature module describes the Protocol Independent Multicast (PIM) Dense Mode (DM) State Refresh feature, which is an extension to the dense operational mode of the PIM Version 2 multicast routing architecture. This feature module includes the following sections:

•Feature Overview

•Supported Platforms

•Supported Standards, MIBs, and RFCs

•Prerequisites

•Configuration Tasks

•Monitoring and Maintaining PIM DM State Refresh

•Configuration Examples

•Command Reference

Feature Overview

PIM dense mode builds source-based multicast distribution trees that operate on a flood and prune principle. Multicast packets from a source are flooded to all areas of a PIM dense mode network. PIM routers that receive multicast packets and have no directly connected multicast group members or PIM neighbors send a prune message back up the source-based distribution tree toward the source of the packets. As a result, subsequent multicast packets are not flooded to pruned branches of the distribution tree. However, the pruned state in PIM dense mode times out approximately every 3 minutes and the entire PIM dense mode network is reflooded with multicast packets and prune messages. This reflooding of unwanted traffic throughout the PIM dense mode network consumes network bandwidth.

The PIM Dense Mode State Refresh feature keeps the pruned state in PIM dense mode from timing out by periodically forwarding a control message down the source-based distribution tree. The control message refreshes the prune state on the outgoing interfaces of each router in the distribution tree.

Benefits

The PIM Dense Mode State Refresh feature keeps the pruned state in PIM dense mode from timing out, which saves network bandwidth by greatly reducing the reflooding of unwanted multicast traffic to pruned branches of the PIM dense mode network. This feature also enables PIM routers in a PIM dense mode multicast network to recognize topology changes (sources joining or leaving a multicast group) before the default 3-minute state refresh timeout period.

Restrictions

All routers in a PIM dense mode network must run a Cisco IOS software release, such as Cisco IOS Release 12.1(5)T, that supports the PIM Dense Mode State Refresh feature to process and forward state refresh control messages.

The origination interval for the state refresh control message must be the same for all PIM routers on the same LAN. Specifically, the same origination interval must be configured on each router interface that is directly connected to the LAN.

Related Features and Technologies

The PIM Dense Mode State Refresh feature is an extension of the PIM Version 2 multicast routing architecture, which is documented in the Release 12.1 Cisco IOS IP and IP Routing Configuration Guide and the Cisco IOS IP and IP Routing Command Reference.

Supported Platforms

The PIM Dense Mode State Refresh feature is supported on the following platforms:

•Cisco 800 series

•Cisco 1400 series

•Cisco 1600 series

•Cisco 1700 series

•Cisco 2500 series

•Cisco 2600 series

•Cisco 3600 series

•Cisco 4000 series (Cisco 4000, 4000-M, 4500, 4500-M, 4700, 4700-M)

•Cisco 7000 series

•Cisco 7200 series

•Cisco 7500 series

•Cisco AS5800 access server

•Cisco AS5400 series

•Cisco AS5300 series

•Cisco AS5200 series

•Cisco MC3810 series

•Cisco MGX8850 WAN edge switch

•Cisco uBR7200 series

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 obtain lists of MIBs supported by platform and Cisco IOS releases, and to download MIB modules, go to the Cisco MIB web site on Cisco Connection Online (CCO) at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.

RFCs

No new or modified RFCs are supported by this feature.

Prerequisites

You must have PIM dense mode enabled on an interface before configuring the PIM Dense Mode State Refresh feature.

Configuration Tasks

There are no configuration tasks for enabling the PIM Dense Mode State Refresh feature. By default, all PIM routers that are running a Cisco IOS software release that supports the PIM Dense Mode State Refresh feature automatically process and forward state refresh control messages. To disable the processing and forwarding of state refresh control messages on a PIM router, use the ip pim state-refresh disable global configuration command.

The origination of state refresh control messages is disabled by default. To configure the origination of the control messages on a PIM router, use the following commands beginning in global configuration mode:

Command
Purpose

Router(config)# interface type number

Specifies an interface and places the router in interface configuration mode.

Router(config-if)# ip pim state-refresh origination-interval [interval]

Configures the origination of the PIM Dense Mode State Refresh control message. Optionally, you can configure the number of seconds between control messages by using the interval argument. The default interval is 60 seconds. The interval range is 4 seconds to 100 seconds.


Verifying PIM Dense Mode State Refresh Configuration

Use the show ip pim interface [type number] detail and the show ip pim neighbor [interface] commands to verify that the PIM Dense Mode State Refresh feature is configured correctly. The following output of the show ip pim interface [type number] detail command indicates that processing, forwarding, and origination of state refresh control messages is enabled. 

Router# show ip pim interface fastethernet 0/1 detail


FastEthernet0/1 is up, line protocol is up

  Internet address is 172.16.8.1/24

  Multicast switching:process

  Multicast packets in/out:0/0

  Multicast boundary:not set

  Multicast TTL threshold:0

  PIM:enabled

    PIM version:2, mode:dense

    PIM DR:172.16.8.1 (this system)

    PIM neighbor count:0

    PIM Hello/Query interval:30 seconds

	PIM State-Refresh processing:enabled

	PIM State-Refresh origination:enabled, interval:60 seconds

    PIM NBMA mode:disabled

    PIM ATM multipoint signalling:disabled

    PIM domain border:disabled

  Multicast Tagswitching:disabled

The S in the Mode field of the following show ip pim neighbor [interface] command output indicates that the neighbor has the PIM Dense Mode State Refresh feature configured. 

Router# show ip pim neighbor


PIM Neighbor Table

Neighbor          Interface          Uptime/Expires    Ver   DR

Address                                                      Priority/Mode

172.16.5.1        Ethernet1/1        00:09:03/00:01:41 v2    1 / B S

Monitoring and Maintaining PIM DM State Refresh

Following are the PIM Dense Mode State Refresh control messages that are sent and received by a PIM router after the debug ip pim privileged EXEC command is configured for multicast group 239.0.0.1: 

Router# debug ip pim 239.0.0.1


*Mar  1 00:25:10.416:PIM:Originating refresh message for

(172.16.8.3,239.0.0.1)

*Mar  1 00:25:10.416:PIM:Send SR on Ethernet1/1 for (172.16.8.3,239.0.0.1)

TTL=9

The following output from the show ip mroute command displays are the resulting prune timer changes for interface Ethernet 1/0 and multicast group 239.0.0.1. (The following output assumes that the debug ip pim privileged EXEC command has already been configured on the router.) In the first output from the show ip mroute command, the prune timer reads 00:02:06. The debug messages indicate that a PIM Dense Mode State Refresh control message is received and sent on Ethernet interface 1/0, and that other PIM Dense Mode State Refresh routers were discovered. In the second output from the show ip mroute command, the prune timer has been reset to 00:02:55. 

Router# show ip mroute 239.0.0.1


(172.16.8.3, 239.0.0.1), 00:09:50/00:02:06, flags:PT

  Incoming interface:Ethernet1/1, RPF nbr 172.16.5.2

  Outgoing interface list:

	Ethernet1/0, Prune/Dense, 00:09:43/00:02:06


Router#

*Mar  1 00:32:06.657:PIM:SR on iif from 172.16.5.2 orig 172.16.8.1 for

(172.16.8.3,239.0.0.1)

*Mar  1 00:32:06.661:     flags:prune-indicator 

*Mar  1 00:32:06.661:PIM:Cached metric is [0/0]

*Mar  1 00:32:06.661:PIM:Keep RPF nbr 172.16.5.2

*Mar  1 00:32:06.661:PIM:Send SR on Ethernet1/0 for (172.16.8.3,239.0.0.1)

TTL=8

*Mar  1 00:32:06.661:     flags:prune-indicator 


Router# show ip mroute 239.0.0.1


(172.16.8.3, 239.0.0.1), 00:10:01/00:02:55, flags:PT

  Incoming interface:Ethernet1/1, RPF nbr 172.16.5.2

  Outgoing interface list:

	Ethernet1/0, Prune/Dense, 00:09:55/00:02:55

Configuration Examples

The following example is for a PIM router that is originating, processing, and forwarding PIM Dense Mode State Refresh control messages on Fast Ethernet interface 0/1 every 60 seconds: 


ip multicast-routing


interface FastEthernet0/1

 ip address 172.16.8.1 255.255.255.0

 ip pim state-refresh origination-interval 60

 ip pim dense-mode

The following example is for a PIM router that is just processing and forwarding PIM Dense Mode State Refresh control messages on Fast Ethernet interface 1/1: 

ip multicast-routing


interface FastEthernet1/1

 ip address 172.16.7.3 255.255.255.0

 ip pim dense-mode

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS IP Multicast Command Reference at http://www.cisco.com/en/US/docs/ios/ipmulti/command/reference/imc_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•ip pim state-refresh disable

•ip pim state-refresh origination-interval

•show ip pim interface


Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

© 2007 Cisco Systems, Inc. All rights reserved.

[an error occurred while processing this directive]