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duplex mode on serial interface

Hi,

I have a simple question. How can I configure and show duplex mode i.e. full or half duplex of serial interface which is running PPP or HDLC? Could anyone please advise?

Thanks,

Nitass

3 ACCEPTED SOLUTIONS

Accepted Solutions
Cisco Employee

Re: duplex mode on serial interface

Hello Nitass,

The serial interfaces are always full-duplex because they are point-to-point and they do not run over a shared medium. If you check the connector pinout you will see that each serial interface has separate Tx and Rx pins and therefore can transmit and receive data simultaneously. Therefore, there is no duplex setting and I believe it would not make sense.

Check this page for pinout details:

http://www.cisco.com/en/US/docs/routers/access/hardware/notes/marcabl.html

Best regards,

Peter

Hall of Fame Super Blue

Re: duplex mode on serial interface

Nitass

You are confusing the data link layer with the physcial layer.

HDLC, which is at the data link layer, can indeed be run in half or full duplex.

However whether or not it does or doesn't largely depends on the capabilities of the underlying physical transmission layer. And as Peter says serial interfaces are point-to-point and so always run at full duplex.

Jon

Hall of Fame Super Gold

Re: duplex mode on serial interface

No, it is not possible to set it.

The only serial protocol that are half-duplex, are SDLC multipoint for IBM networking. Legacy thing not of interest to us.

6 REPLIES
New Member

Re: duplex mode on serial interface

Hi

Unless someone can prove otherwise, there is no duplex setting as you don't run ethernet over serial.

Why di you think you need it?

Kev

Cisco Employee

Re: duplex mode on serial interface

Hello Nitass,

The serial interfaces are always full-duplex because they are point-to-point and they do not run over a shared medium. If you check the connector pinout you will see that each serial interface has separate Tx and Rx pins and therefore can transmit and receive data simultaneously. Therefore, there is no duplex setting and I believe it would not make sense.

Check this page for pinout details:

http://www.cisco.com/en/US/docs/routers/access/hardware/notes/marcabl.html

Best regards,

Peter

New Member

Re: duplex mode on serial interface

Hello,

I have seen some web mentioned that PPP and HDLC support either half or full duplex mode but I have not seen any commands except only "half-duplex timer" under interface serial. So, I think it might be possible to set it.

Please let me know if I misunderstood anything.

Thank you very much,

Nitass

Hall of Fame Super Blue

Re: duplex mode on serial interface

Nitass

You are confusing the data link layer with the physcial layer.

HDLC, which is at the data link layer, can indeed be run in half or full duplex.

However whether or not it does or doesn't largely depends on the capabilities of the underlying physical transmission layer. And as Peter says serial interfaces are point-to-point and so always run at full duplex.

Jon

Hall of Fame Super Gold

Re: duplex mode on serial interface

No, it is not possible to set it.

The only serial protocol that are half-duplex, are SDLC multipoint for IBM networking. Legacy thing not of interest to us.

New Member

Re: duplex mode on serial interface

I got it. I am so appreciated for your help. :-)

Thanks,

Nitass

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