PPP

Features:

• Synchronous and asynchronous links.


• Consist of 3 protocols: HDLC, LCP, NCP


• A protocol type in the header


• Built-in authentication CHAP, PAP(controlled by LCP - Link Control Protocol).


• Control protocols for each higher level protocols.


• It uses Control Protocol (CP) for controlling Layer 3 protocols and LCP for link configuration.

LCP features:

• Magic number for looped link detection. The link may be looped, this means, that router receives back info, that it sent. Router detects loop by using magic number in LCP message. Every router has it's own magic number.


• Link Quality Monitoring (LQM) for error detection


• Multilink PPP for multilink support


• Multilink Starting with IOS version 11.1, multilink is supported on PPP links with Cisco routers. This option makes several separate physical paths appear to be one logical path at layer 3. For example, two T1s running multilink PPP would show up as a single 3Mbps path to a layer 3 routing protocol.

PAP and CHAP for authentication

Configure PPP:

hostname R1

interface s0/0

encapsulation ppp

ppp authentication chap

username remote_hostname password 0 share_password

Troubleshoot ppp:

debug ppp authentication

Very detailed explonation of how chap authentication works on Cisco routers:

http://www.ciscosystems.com/en/US/tech/tk713/tk507/technologies_tech_note09186a00800b4131.shtml

Configure PPPoE:

R1(config)#int f0/0

R1(config-if)#pppoe enable group global

R1(config-if)#pppoe-client dial-pool-number 1

interface Dialer0

ip address negotiated

ip mtu 1452

encapsulation ppp

dialer pool 1

dialer-group 1

ppp authentication chap callin

ppp chap hostname host

ppp chap password 0 pass