This applies to classic CLI.
To enter the mode to edit timing references, you must enter the begin keyword.
Use the following classic CLI command to enter the edit mode:
config>system>sync-if-timing# begin
The following error message shows when the you try to modify sync-if-timing parameters without entering the keyword begin.
A:ALA-12>config>system>sync-if-timing>ref1# source-port 2/1/1
MINOR: CLI The sync-if-timing must be in edit mode by calling begin before any
changes can be made.
MINOR: CLI Unable to set source port for ref1 to 2/1/1
A:ALA-12>config>system>sync-if-timing>ref1#