HDLC Configuration on Cisco


In this HDLC lesson, we will learn Cisco HDLC Configuration on Cisco Routers. We will learn the required Cisco commands to configure Cisco HDLC.


HDLC is a point-to-point protocol and it is the default protocol for serail interfaces on Cisco routers. HDLC is a standard poin-to-point protocol. But, here there is an important point. Between two different vendor devices, we can not configure HDLC. Because, for HDLC, different vendors has different proprietary field. In other words, Cisco uses different proprietary field and Huawei uses different proprietary  field for this purposes. Because of these differences, we can not configure HDLC between different vendors.


For our Cisco HDLC Configuration example, we will use the below basic topology.  As you can see below, there are tweo routers and we will configure HDLC between these routers on each end.



For this example, we will use prefix for IP addressing. One end will be and the other will be

Now, let’s start to configure Cisco HDLC for this topology.


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Enabling Cisco HDLC

To configure Cisco HDLC, firstly we will enable HDLC under the interface and after that, we will configure interface ip addresses. To enable HDLC, we will use “encapsulation hdlc” command under the interface. Here, we will do this under serial 0/0/0 interface.

Router1# configure terminal
Router1(config) # interface Serial 0/0/0
Router1(config-if) # encapsulation hdlc
Router1(config-if) # ip address
Router1(config-if) # exit


We will do the same configuration, on Router 2 like below:


Router2# configure terminal
Router2(config) # interface Serial 0/0/0
Router2(config-if) # encapsulation hdlc
Router2(config-if) # ip address
Router2(config-if) # exit



Verifying Cisco HDLC

To verify Cisco HDLC configuration,on both routers we will use “show ip interface serial” command. The output of this command willl give us the point-to-point protocol in one line. As you can see below, for this configuration example, it is HDLC.


Router1# show ip interface serial 0/0/0
Serial0/0/0 is up, line protocol is up
Encapsulation HDLC,


Router2# show ip interface serial 0/0/0
Serial0/0/0 is up, line protocol is up
Encapsulation HDLC,


In this Cisco HDLC Example, we have learned how to configure HDLC on Cisco routers.


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Lesson tags: cisco IOS, packet tracer, cisco packet tracer, wan
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