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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 local. Use the set portclockmode command to change
a ports clocking source. For example, the following sets port
5a3 into loopback mode.
SmartSwitch # set portclockmode
PortNumber(ALL) : 5a3
PortClkMode(local) : loop
SmartSwitch #
Note 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
set networkclock 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
7a1 to a service provider’s switch that produces a high-precision clocking signal.
1. Use the set networkclock command to specify the port through which the network clocking signal
is to be obtained
SmartSwitch # set networkclock
PortNumber(none) : 7a1
SmartSwitch #
2. Use the set portclockmode command to instruct ports (either all ports or on a per-port basis) to use
the clocking signal obtained from port
7a1
SmartSwitch # set portclockmode
PortNumber(ALL) :
— In this example, we set all ports to use the network clock
PortClkMode(local) : network
SmartSwitch #
Once the set portclockmode command is entered with the PortClkMode parameter set to network, the ports specified
on the SmartSwitch 6500 now use the clocking signal received on port
7a1 as their port clock source.