PPP Notes

PPP stands for Point-to-Point Protocol. It is a data link layer (Layer 2) protocol used to establish a direct connection between two nodes or devices over a serial link. PPP is commonly used for connecting a computer or network device to the Internet via dial-up connections, DSL (Digital Subscriber Line) connections, and other types of serial links.

Key features of PPP include:

1. **Authentication**: PPP supports various authentication methods, including Password Authentication Protocol (PAP), Challenge Handshake Authentication Protocol (CHAP), and Extensible Authentication Protocol (EAP). These authentication mechanisms allow the two nodes to authenticate each other before establishing a connection.

2. **Error Detection and Correction**: PPP includes mechanisms for detecting and correcting errors that may occur during data transmission. These mechanisms help ensure the integrity of data transmitted over the PPP link.

3. **Multilink PPP (MLPPP)**: MLPPP is an extension of PPP that allows multiple physical links to be bonded together to increase bandwidth and redundancy. MLPPP aggregates the bandwidth of multiple links into a single logical connection, providing higher throughput and fault tolerance.

4. **Network Protocol Support**: PPP can encapsulate various network layer protocols, including IPv4, IPv6, IPX, and AppleTalk. This allows PPP to be used with a wide range of network protocols and environments.

5. **Link Control Protocol (LCP)**: LCP is a core component of PPP responsible for establishing, configuring, and terminating PPP connections. LCP negotiates link parameters such as authentication methods, compression options, and network layer protocol settings.

6. **Network Control Protocols (NCPs)**: NCPs are used in conjunction with LCP to negotiate and configure network layer protocols. Each network layer protocol (e.g., IPv4, IPv6) has its own NCP for configuring protocol-specific parameters.

Overall, PPP is a widely used protocol for establishing point-to-point connections over serial links, providing features such as authentication, error detection, and support for multiple network layer protocols. It is commonly used in scenarios where direct serial connections are required, such as dial-up Internet access, DSL connections, and serial links between network devices.

PPP

====

Media independent encapsulation

-serial, Ethernet, frame realy, ATM, etc

-encapsulation ppp

Addds features that other layer2 medias don’t support

-Authentication

-multilink

-fragmentation

-reliability

PPP uses link control protocol(LCP) to negotiate higher layer protocols

-          Internet protocol control protocol (IPCP)

-          IPV6CP

-          -CDPCP

-          ETC

Can be used to negotiate

-          Address assignment

-          Routing information

Verification

-          Debug ppp negotiation

Note: with ppp we don’t care about direction since connection will always be a dedicated line.

PPP Authentication

================

Password Authentication protocol (PAP)

-          Clear text username

-          Clear text password

Challenge Handshake Authentication Protocol (CHAP)

-          Clear text username

-          MD5 hashed password

MSCHAP/MSCHAPv2/EAP/ etc

PPP PAP Authentication

==================

Authentication Request

-ppp authentication pap

Authentication response

-no ppp pap refuse

-ppp pap sent-username.. password

Verification

-debug ppp negotiation

-debug ppp authentication

Ppp auth pap command in router1 is independent of ppp auth pap command in another router. It need not to be same on both routers.

PPP CHAP Authentication

========================

Authentication request

-ppp autrhentication chap

Authentication response

-no ppp chap refuse

-username and passwords

   Global vs interface

Verification :

-debug ppp negotiation

-debug ppp authentication

PPP over Ethernet Server

======================

Define PPP interface

-interface virtual-template [num]

Apply logical options

-Authentication, multilink, IP address etc.

Define BBA Group

-bba-group pppoe [name | global]

-virtual-template [num]

Bind to link

-ppoe enable group [name | global}

PPP over Ethernet Client

========================

Define PPP interface

-interface dialer [num]

-encapsulation ppp

-dialer pool [pool]

-dialer group | dialer persistent

Apply logical options

-Authentication, multilink, IP address etc

Bind to link

-pppoe-client dial-pool-number [pool]