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Example: Modifying the MLD Robustness Variable

This example shows how to configure and verify the MLD robustness variable in a multicast domain.

Requirements

Before you begin:

Overview

The MLD robustness variable can be fine-tuned to allow for expected packet loss on a subnet. Increasing the robust count allows for more packet loss but increases the leave latency of the subnetwork.

The value of the robustness variable is used in calculating the following MLD message intervals:

  • Group member interval—Amount of time that must pass before a multicast router determines that there are no more members of a group on a network. This interval is calculated as follows: (robustness variable x query-interval) + (1 x query-response-interval).
  • Other querier present interval—Amount of time that must pass before a multicast router determines that there is no longer another multicast router that is the querier. This interval is calculated as follows: (robustness variable x query-interval) + (0.5 x query-response-interval).
  • Last-member query count—Number of group-specific queries sent before the router assumes there are no local members of a group. The default number is the value of the robustness variable.

By default, the robustness variable is set to 2. The number can be from 2 through 10. You might want to increase this value if you expect a subnet to lose packets.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

set protocols mld robust-count 5

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To change the value of the robustness variable:

  1. Configure the robust count.

    [edit protocols mld]user@host# set robust-count 5

  2. If you are done configuring the device, commit the configuration.

    [edit protocols mld]user@host# commit

Verification

To verify the configuration is working properly, check the MLD Robustness Count field in the output of the show mld interfaces command.

 

Related Documentation

 

Published: 2012-11-16

Supported Platforms

 

Related Documentation

 

Published: 2012-11-16

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