Point-to-Point Protocol (PPP)

Serial ports do not have MAC address. The question is how the serial connection works then if it does not have MAC address because at the end of the day we have to have layer-2 transimission.

There are other technologies such as PPP, HDLC, Frame-Realy, and MPLS that work on layer-2 in serial connection.

Frame-relay and MPLS are two protocols that isolate the data of multiple customers using a single line.

PPP is the technology that ensures that you own the equipments and line, no one other than you can use the line to transmit data and the transmission will be secure. PPP is super easy to configure and is still used.
PPP is layer-2 protocol.

PPP has many other child protocols that run together or separately to run PPP.
LCP is Link Control Protocol that controls the link connection.
IPCP is Internet Protocol Control Protocol that handles the IP configuration.


HDLC is Cisco proprietary and it is on by default in Cisco routers, it fast but it does not support many features.

PPP is open standard, it is a suite of multiple protocols. It has vast amount of features including authentication, redundancy, link-aggregation, and other.


PPP is just only to send the frame from one router to the another without the interference of any other party.

Exploring the above diagram when a packet comes from R6 to R5, R5 takes out the frame and sends the frame to R3 now R3 takes the frame and forwards it to the next destionation. PPP is temporary transmission when there are two PPP technologies at both ends.

PPP Configuration


Notice that to be able to run PPP the encapsulation should be set to ppp on both sides because by default the encapsulation is set to hdlc.



PPP Authentication

We can set the authentication mechanism and the routers will be authenticated when the links come up.
We have to create a user for this authentication at both ends and the user name should be adjacent meaning that if we configure this on R1 and R2. The username on R1 would be R2 because we are going to authenticate R2 not our self and same thing for another router. The passwords at both ends should be exactly same to get authentication successful


Notice that we are creating a user for R5 and as soon as we trigger the authentication technology the interface goes down and the LCP status changes to close.



Notice that on R5 we are creating user of R3 and the passwords remains same.

The authentication technology requires that the username should be name of neighbor router and it is case-sensitive.

LAB Topology


Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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