What does Clock Rate affect?

[JoshGarmonCiscoCCNA]

On a serial interface, what does it do?

What happens the higher you make it? lowerer you make it?

Does the Clock Rate affect PPP, HDLC, and Frame Relay encapsulation?

I was in Packet Tracer using two 819 Routers and a Serial link between them.

I configured PPP Pap encapsulation/authentication between each and put clock rate 128000 on the DCE side.

Could not ping between them yet they were DIRECTLY connected.

I then removed PPP encapsulation altogether AND dropped the clock rate down to just 19200

Ping finally worked.

So I don't know which change fixed this.

[Masoud Pourshabanian]

Hello,

You do not need to set clock rate in test environment. Clock rate is usually set on modems to synchronize sender and receiver signals.  Then modems connect to routers.

In Packet Tracer just use DTE cable for both sides.

Clock rate is for synchronizing the layer 1 signals and not related to PPP or HDLC

Something like this in real world.

Router   ---- modem---- leased line----modem--Router

[Richard Bradfield]

What was the serial link you were using on  the 2 819s aux port?

[JoshGarmonCiscoCCNA]

Thanks Masoud.

Richard, the interface was Serial 0.

On the 819's, Serial 0 is the only Serial interface avaiable.

[Masoud Pourshabanian]

You are welcome.

Please choose the answers as correct if you are pleased with the answers. Thanks

[Joseph W. Doherty · Accepted solution]

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Posting

Many serial interfaces require a clock signal.  Normally, this would be provided by the Telcom's DCE, however, in a lab, if you put two routers back-to-back, you'll need to configure one side (and only one side) with clock rate.

Clock rate determines the actual data transfer rate.