Clock Source Network vs Internal vs Line

[Tom W.]

Does anybody know what's the difference between clock source network, internal vs line?

Thanks.

[Roger Kallberg]

Please have a look at this document, it explains clocking setup in Cisco 4K ISR, but is for your question also applicable for other platforms. https://community.cisco.com/t5/collaboration-voice-and-video/t1-pri-line-clock-design-considerations-on-isr4k/ta-p/3163800

[Tom W.]

"clock source line [primary|secondary]

　　Configures the clock source of the backplane

clock source network

　 Uses the backplane clock or the oscillator clock as the module clock source

Note: The command 'clock source internal' is used for data transmission, not for voice transmission."

So from this quoted from the document if the T1/E1 is used for data use 'clock source internal' and it's used for voice ( PRI ) then use 'clock source network'?

[Roger Kallberg · Accepted solution]

Not quite, the most common configuration for voice would be to use the line as the source of clock.