`ip pim-dense ttl-threshold`

Syntax

ip pim-dense ttl-threshold <THRESHOLD-VALUE>

no ip pim-dense ttl-threshold

Description

Configures the multicast datagram time-to-live (router hop-count) threshold for the interface. A state-refresh packet with a TTL less than this threshold will not be forwarded out the interface.

The no form of this command removes the currently configured value and sets to the default of 3 attempts.

Command context

config-if

config-if-vlan

config-lag-if

Parameters

<THRESHOLD-VALUE>: Specifies the time to live threshold. Default: 3 attempts. Range: 0-255.

Authority

Administrators or local user group members with execution rights for this command.

Usage

The interface connected to the multicast source does not receive state refresh packets and thus is not state-refresh capable. Downstream VLANs in the switches are state-refresh capable. This parameter provides a method for containing multicast traffic within a network, or even within specific areas of a network. Initially, the multicast traffic source sets a TTL value in the packets it transmits. Each time one of these packets passes through a multicast routing device, the TTL setting decrements by 1. If the packet arrives with a TTL lower than the ttl-threshold, the routing switch does not forward the packet. The following aspects of the TTL setting of incoming multicast packets must be considered, before changing this parameter on a routing switch:

A value that is too high will allow multicast traffic to go beyond the internal network.
A value that is too low may prevent some intended hosts from receiving the desired multicast traffic.
A value of 0 will forward multicast traffic regardless of the packet TTL setting.

Example

Configuring and removing the time to live threshold:

switch(config)# interface vlan40
switch(config-if-vlan)# ip pim-dense ttl-threshold 8
switch(config-if-vlan)# no ip pim-dense ttl-threshold