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8-4   SmartSwitch ATM User Guide

Port Clock Configuration

  ATM Filtering and Clocking

By default, the clock mode for all SmartSwitch 6500 ports is 

. Use the 

 command to change 

a ports clocking source. For example, the following sets port 

 into loopback mode.

SmartSwitch # set portclockmode

PortNumber(ALL)                           : 5a3

PortClkMode(local)                        : loop

SmartSwitch #

Never configure two connecting port to both be in loopback mode. Without at 
least one of the connecting ports generating a clocking signal, connectivity will go 
out of sync and communication will be lost.

8.2.1

Network Clocking

Network clocking allows your SmartSwitch 6500 to obtain an external, high-quality, precise clocking signal and make 
it available for use by all ports. Typically, network clocking is configured when a high-quality clock signal is available 
(for example from a service provider connection) and the SmartSwitch is supporting traffic from applications that are 
time-sensitive, such as voice and video. The port connected to the high-precision clock signal is specified as the 
network source using the 

 command. When set, the port is essentially placed in loopback mode, 

however, the port also places the incoming, high-precision signal on the SmartSwitch 6500’s backplane, where it 
becomes available to all other ports.

The following is an example of network clocking configuration. It is assumed in this example that the SmartSwitch 
6500 is connected through port 

 to a service provider’s switch that produces a high-precision clocking signal.

Use the 

 command to specify the port through which the network clocking signal 

is to be obtained

SmartSwitch # set networkclock

PortNumber(none)                          : 7a1

SmartSwitch #

Use the 

 command to instruct ports (either all ports or on a per-port basis) to use 

the clocking signal obtained from port 

SmartSwitch # set portclockmode

PortNumber(ALL)                           : 

PortClkMode(local)                        : network

SmartSwitch #

Once the 

 command is entered with the 

 parameter set to 

, the ports specified 

on the SmartSwitch 6500 now use the clocking signal received on port 

as their port clock source.