WAN Circuits
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In This Section
» HDLC
» PPP • PPP Negotiation
• PPP Authentication
• PPP over Ethernet
• Misc. PPP Features
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High-Level Data Link Control (HDLC)
» Default serial encapsulation
» Does not support any advanced features
» Has problems with vendor interoperability
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Point-to-Point Protocol (PPP)
» Media independent encapsulation • Serial, Ethernet, Frame Relay, ATM, etc.
» Better choice for interoperability » Adds features that other layer 2 medias don’t
natively support • Authentication • Multilink • Fragmentation • Reliability • Compression
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PPP Negotiation
» 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
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PPP Authentication
» PPP Authentication adds security to encapsulations that don’t normally support it • E.g. PPPoE over DSL/ATM with CHAP Authentication
» Multiple authentication varieties • PAP
• CHAP
• MSCHAP
• EAP
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PPP Authentication Methods
» 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…
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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
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PPP CHAP Authentication
» Authentication Request • ppp authentication chap
» Authentication Response • no ppp chap refuse • Usernames & Passwords • Global vs Interface
» Verification • debug ppp negotiation • debug ppp authentication
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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 • pppoe enable group [name | global]
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PPP over Ethernet Client
» Define PPP interface • interface dialer [num] • encapsulation ppp • dialer pool [pool]
» Apply logical options • Authentication, multilink, IP address, etc.
» Bind to link • pppoe-client dial-pool-number [pool]
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Q&A