Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 453
53-1002269-02
Configuring PIM SM snooping
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Syntax: [no] multicast fast-leave-v2
Fast convergence
In addition to sending periodic general queries, an active device sends general queries when it
detects a new port. However, because the device does not recognize the other device's port up
event, multicast traffic might still require up to the query-interval time to resume after a topology
change. Fast convergence allows the device to listen to topology change events in Layer 2 protocols
such as spanning tree, and then send general queries to shorten the convergence time.
If the Layer 2 protocol cannot detect a topology change, fast convergence may not work in some
cases. For example, if the direct connection between two devices switches from one interface to
another, the rapid spanning tree protocol (802.1w) considers this optimization, rather than a
topology change. In this example, other devices will not receive topology change notifications, and
will be unable to send queries to speed up the convergence. Fast convergence works well with the
regular spanning tree protocol in this case.
Enabling Fast convergence
To enable fast-convergency, enter the following commands.
PowerConnect(config)# vlan 70
PowerConnect(config-vlan-70)# multicast fast-convergence
Syntax: multicast fast-convergence
Configuring PIM SM snooping
Configuring PIM SM snooping on a device consists of the following global and VLAN-specific tasks.
Global task
Perform the following global tasks:
• “Enabling or disabling PIM SM snooping”
VLAN-specific tasks
Perform the following VLAN-specific tasks:
• “Enabling PIM SM snooping on a VLAN”
• “Disabling PIM SM snooping on a VLAN”
Enabling or disabling PIM SM snooping
PIM SM snooping should be used only in topologies where multiple PIM sparse routers connect
through a device. PIM SM snooping does not work on a PIM dense mode router which does not
send join messages, and traffic to PIM dense ports is stopped. A PIM SM snooping-enabled device
displays a warning if it receives PIM dense join/prune messages.
To enable PIM sparse snooping globally, enter a command such as the following.
PowerConnect(config)# ip pimsm-snooping
This command enables PIM SM traffic snooping. The PIM SM traffic snooping feature
assumes that the network has routers that are running PIM SM.