WAN Circuits

HDLC:
- default serial encapsulation
- no advanced features
- problems with vendor interoperability
- very easy config "no shut", configure clockrate

HDLC

PPP:
- negotiation, authentication (PAP, CHAP), PPPoE
- easy to configure, 'encapsulation ppp'
- debug ppp negotiation
- pap: password authentication protocol
- challenger: "ppp authentication pap"
- reponse: "no ppp pap refuse", "ppp pap sent-username... password"

PPP