How to configure HDLC on Cisco IOS Router

This topic is to discuss the following lesson:

H Rene

I set up similar set up in my GNS3 lab, R1 and R2. Set R2 with a clock rate for the serial interface but R1 is not showing as a DTE. I assigned the IP address and I can ping the interfaces but DTE is not showing on R1. Any reason can you think of? How can I troubleshoot this issue?

R1#sh controllers s0/0
Interface Serial0/0
Hardware is PowerQUICC MPC860
DCE 530, no clock
R2#sh controllers s0/0
Interface Serial0/0
Hardware is PowerQUICC MPC860
DCE 530, clock rate 64000


Hi Palani,

Setting the clock rate is for the physical interface. In GNS3, there’s no need to set the clock rate since they emulate everything. If you want to test this, you will have to use real hardware.


Hi Rene,

Is HDLC encapsulation only for serial interfaces ? I have seen it on Ethernet interface as well

Hello Aniket

HDLC is an encapsulation method that provides layer 2 functionality almost exclusively for point to point connections. Point to multipoint connections are also possible but are rarely used. Ethernet on the other hand is a layer 2 technology based on a multiple access philosophy. These are two very different and incompatible technologies, both of which operate at layer 2, so HDLC cannot operate on an Ethernet interface.

Do you have an example of what you have seen concerning HDLC and Ethernet? Maybe that will help to clarify the confusion. If you do, share it with us so we can continue the conversation.

I hope this has been helpful!


Is there a criteria for setting the clock rate to 64? Most of the examples are 64. Why??

Hello YongHun

The clock rate for a serial interface determines the bandwidth of the serial connection. The clock rate must be specified on the DCE side of the connection. The value can be any supported value. The fact that 64000 is used often probably has to do with convenience or coincidence. There is no particular significance to this value.

More info on this command can be found here:

I hope this has been helpful!


Hi Lazaros,

I found myself in the CCNA Routing & Switching ICND2 200-105 for what I am guessing is the old CCNA, but it was puzzling because it looks like it went into OSPFv3, EIGRP (in great depth) and also BGP. Are we supposed to also know that content for the new CCNA cert and if so why isn’t it in the new course for CCNA 201-300?

Hello Daniel

The content that is covered in the CCNA 201-300 can be found on the following course page:

You may find that some of these lessons are also under the older ICND1 and ICND2 course pages and categories because the content was in those courses as well. However, the official topics are found in the course site I sent above.

To see the official list of covered material, take a look at Cisco’s official list at the following link:
You will see that this aligns well with the course page I shared above.

I hope this has been helpful!


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Thank you Lazaros! I only asked because I have heard some people take the test and say there was some EIGRP or other periphery references so I just wanted to make sure

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