3Com 9000 manual SP2 Set External Clock Source

Setting Up the Switch Clock Source 109

Set External Clock	Set a port to be the second external clock source port. If the port does
Source 2	not exist, is disabled, is in loop timing mode, loopback or loop forward, it
	cannot be used as an external clock source port.
	Command Actions
	Enter menu sequence:	(1) SYS: Platform Configuration
		(8) SCS: Switch Clock Synchronization
		Setup
		(3) SP2: Set External Clock Source 2
	Enter parameter at prompt
	Parameter	Format or Range
	Clock source	<slot.group.port> or None
	Direct access sequence:	1 8 3 [parameter]
	Command Result
	System action:	The port is set to be the active clock source port.
	System message display:	External clock source port 2 was
		successfully configured to port
		<slot.group.port>.

If the port has already been set to be the first or second clock source, it is meaningless to set the port again. In this case, the command is ignored and the following message is displayed:

Clock source 1 is already set to this port.

It is meaningless to set the two sources to the same port, operation ignored.