Example: Enabling Join Suppression

This example describes how to enable PIM join suppression.

Requirements

Before you begin:

Configure the router interfaces. See the Network Interfaces Configuration Guide.
Configure an interior gateway protocol or static routing. See the Routing Protocols Configuration Guide.
Configure PIM Sparse Mode on the interfaces. See Enabling PIM Sparse Mode.

Overview

PIM join suppression enables a router on a multiaccess network to defer sending join messages to an upstream router when it sees identical join messages on the same network. Eventually, only one router sends these join messages and the other routers suppress identical messages. Limiting the number of join messages improves scalability and efficiency by reducing the number of messages sent to the same router.

This example includes the following settings:

override-interval—Sets the maximum time in milliseconds to delay sending override join messages. When a router sees a prune message for a join it is currently suppressing, it waits before it sends an override join message. Waiting helps avoid multiple downstream routers sending override join messages at the same time. This is a random timer with a value of 0 through the maximum override value.
propagation-delay—Sets a value in milliseconds for a prune pending timer, which specifies how long to wait before executing a prune on an upstream router. During this period, the router waits for any prune override join messages that might be currently suppressed. The period for the prune pending timer is the sum of the override-interval value and the value specified for propagation-delay.
reset-tracking-bit—Enables PIM join suppression on each multiaccess downstream interface. This statement resets a tracking bit field (T-bit) on the LAN prune delay hello option from the default of 1 (join suppression disabled) to 0 (join suppression enabled).
When multiple identical join messages are received, a random join suppression timer is activated, with a range of 66 through 84 milliseconds. The timer is reset each time join suppression is triggered.

Figure 10 shows the topology used in this example.

Figure 10: Join Suppression

Image g040619.gif

The items in the figure represent the following functions:

H0 is the multicast source.
H1, H2, H3, and H4 are receivers.
R0 is the first-hop router and the RP.
R1 is an upstream router.
R2, R3, R4, and R5 are downstream routers in the multicast LAN.

Configuration

CLI Quick Configuration

To quickly configure PIM join suppression on a downstream router, copy the following commands and paste them into the CLI.

[edit]set protocols pim traceoptions file pim.log set protocols pim traceoptions file size 5m set protocols pim traceoptions file world-readable set protocols pim traceoptions flag join detail set protocols pim traceoptions flag prune detail set protocols pim traceoptions flag normal detail set protocols pim traceoptions flag register detail set protocols pim rp static address 10.255.112.160 set protocols pim interface all mode sparse set protocols pim interface all version 2 set protocols pim interface fxp0.0 disable set protocols pim reset-tracking-bit set protocols pim propagation-delay 500 set protocols pim override-interval 4000

Step-by-Step Procedure

To configure PIM join suppression on a non-RP downstream router in the multicast LAN:

Configure PIM.
[edit]user@host# edit protocols pim[edit protocols pim]user@host# set rp static address 10.255.112.160[edit protocols pim]user@host# set interface all mode sparse version 2[edit protocols pim]user@host# set interface all version 2[edit protocols pim]user@host# set interface fxp0.0 disable
Enable the join suppression timer.
[edit protocols pim]user@host# set reset-tracking-bit
Configure the prune override interval value.
[edit protocols pim]user@host# set override-interval 4000
Configure the propagation delay of the link.
[edit protocols pim]user@host# set propagation-delay 500
(Optional) Configure PIM tracing operations.
[edit protocols pim]user@host# set traceoptions file pim.log size 5m world-readable[edit protocols pim]user@host# set traceoptions flag join detail[edit protocols pim]user@host# set traceoptions flag join detail[edit protocols pim]user@host# set traceoptions flag normal detail[edit protocols pim]user@host# set traceoptions flag register detail
If you are done configuring the device, commit the configuration.
[edit protocols pim]user@host# commit

Results

From configuration mode, confirm your configuration by entering the show protocols commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

user@host# show protocolspim {traceoptions {file pim.log size 5m world-readable;flag join detail;flag prune detail;flag normal detail;flag register detail;}rp {static {address 10.255.112.160;}}interface all {mode sparse;version 2;}interface fxp0.0 {disable;}reset-tracking-bit;propagation-delay 500;override-interval 4000;}

Verification

To verify the configuration, run the following commands on the upstream and downstream routers:

show pim join extensive
show multicast route extensive