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Question about clockrate, DTE/DCE - unable to remove clock rate

Hello folks

I'm currently preparing a new 1841 with a HWIC-1T serial interface. I need to preconfigure the router which will then be shipped to where it is going to be used. The router currently does not have a serial connection attached to it (as I don't have a serial connection).

I've reached the configuration of the serial interface and I'm having some problems removing the "clock rate 2000000" command to make it a DTE.

I've tried the following commands:

no clock rate

no clock rate 2000000

default clock rate

We already have a router onsite with a working serial interface and that one does not have any clock rate set.

Can anyone help me here? :/

Thanks in advance

-- Jesper

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Question about clockrate, DTE/DCE - unable to remove clock r

Hello Jesper,

The clock rate command is added in newer IOS versions automatically to the interface and cannot be removed manually. It will be automatically removed if you connect the DTE cable to the serial interface. So don't worry about that command being present in the configuration right now. It will disappear automatically when a DTE cable is plugged to the port.

Note that a serial interface cannot be configured to work in Layer1 DCE or DTE mode by command. This depends exclusively on the type of the cable. Most certainly, the clock rate command simply sets the clockrate to be used if a DCE-type cable is connected. Otherwise, that command is ignored.

In older IOSes, the command could actually be removed from the interface but that was a source of common configuration mistake - both routers connected, interfaces went up but line protocol remained down because the clock rate was not set and thus data could not be carried through the synchronous serial link. Therefore, newer IOSes add the clockrate setting automatically (set to a sensible default).

So to put it short - if the router is going to be the DTE, simply ignore the clockrate command

Best regards,

Peter

3 REPLIES
Cisco Employee

Re: Question about clockrate, DTE/DCE - unable to remove clock r

Hello Jesper,

The clock rate command is added in newer IOS versions automatically to the interface and cannot be removed manually. It will be automatically removed if you connect the DTE cable to the serial interface. So don't worry about that command being present in the configuration right now. It will disappear automatically when a DTE cable is plugged to the port.

Note that a serial interface cannot be configured to work in Layer1 DCE or DTE mode by command. This depends exclusively on the type of the cable. Most certainly, the clock rate command simply sets the clockrate to be used if a DCE-type cable is connected. Otherwise, that command is ignored.

In older IOSes, the command could actually be removed from the interface but that was a source of common configuration mistake - both routers connected, interfaces went up but line protocol remained down because the clock rate was not set and thus data could not be carried through the synchronous serial link. Therefore, newer IOSes add the clockrate setting automatically (set to a sensible default).

So to put it short - if the router is going to be the DTE, simply ignore the clockrate command

Best regards,

Peter

New Member

Re: Question about clockrate, DTE/DCE - unable to remove clock r

Hello Peter

Thank you so much for your answer. It helped me alot.

I thought it was something like that.

Have a nice day

Cisco Employee

Re: Question about clockrate, DTE/DCE - unable to remove clock r

Hi Jesper,

You are heartily welcome. Have a great day, too!

Best regards,

Peter

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