PPP – Point to Point Protocol
– Standardized protocol
– Supports synchronous and asynchronous links
– Authentication with the PAP and CHAP protocols.
Before starting this article, please start with the article on HDLC, this protocol is the "ancestor" of the PPP. It is therefore important to know how it works to fully understand the PPP.
PPP control protocol
The Ethernet protocol includes other Level 2 protocols to perform different roles (such as Spanning tree).
In the PPP protocol, there are two types of protocols:
– LCP (Link Control Protocol)
Error Detection (LQM – Link-Quality Monitoring)
Link aggregation (Multilink PPP)
Authentication (PAP and CHAP)
– ASC (Network Control Protocols)
There are two authentication protocols for PPP:
– PAP (Authentication Password Protocol)
The password in clear on the network
– CHAP (Challenge Hand-shake Authentication Protocol)
The password does not circulate in plain sight on the network
The CHAP protocol is therefore the protocol to choose in terms of PPP authentication. /!
Activation of ppp protocol
As we saw for the HDLC protocol: we need to configure our router's serial interface as follows:
Router (config) - serial interface 0/0/0 Router (config-if) ip address X.X.X.X X.X.X.X
This serial link will automatically choose the HDLC protocol. Since we want to use the PPP protocol, we need to add the following command:
Router (config-if) ppp encapsulation
The protocol must be the same on both sides of the Serial link!!
Introducing PAP authentication
Introducing CHAP authentication
The R1 and R2 passwords must be the same!
MultiLink PPP implementation
The multilink PPP will work in the same way as the Etherchannel.
It allows you to "merge" several links into one.
Let's take the following example:
We can see 2 serial links between R1 and R2. At the routing level, we're going to have to make sure that our dynamic routing protocol can do load-balancing (either with OSPF by putting an equal metric on both links or using EIGRP).
To do this we will do as in the following example:
Importantpoint: the number of the Multilink group must be the same on our two configurations, on all our serial interfaces as well as on our two multilink interfaces.
Hoping this article has been helpful to you! Don't hesitate to let me know!!
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