Transcript NetAdmin

CCNA Guide to Cisco
Networking Fundamentals
Fourth Edition
Chapter 11
PPP and HDLC
Objectives
•
•
•
•
Describe PPP encapsulation
Configure PPP encapsulation and its options
Describe and enable PPP multilink
Understand Frame Relay standards and equipment
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
2
Objectives (continued)
• Describe the role of virtual circuits and performance
parameters in Frame Relay
• Understand the Frame Relay topologies
• Understand the difference between multipoint and
point-to-point configurations
• Configure and monitor Frame Relay
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
3
PPP
• PPP
– Internet standard protocol defined in RFCs 2153 and
1661
– Provide point-to-point, router-to-router, host-to-router,
and host-to-host connections
– Considered a peer technology based on its point-topoint physical configuration
– Commonly used over dial-up or leased lines to provide
connections into IP networks
• Serial Line Internet Protocol (SLIP) was the
predecessor to PPP
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
4
PPP (continued)
• PPP can be used over several different physical
interfaces, including the following:
– Asynchronous serial
– ISDN synchronous serial
– High-Speed Serial Interface (HSSI)
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
5
PPP in the Protocol Stack
• You can use PPP over both asynchronous and
synchronous connections
– At the Physical layer of the OSI reference model
• Link Control Protocol (LCP)
– Used at the Data Link layer to establish, configure,
and test the connection
• Network Control Protocols (NCPs)
– Allow the simultaneous use of multiple Network layer
protocols and are required for each protocol that uses
PPP
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
6
PPP in the Protocol Stack (continued)
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
7
Frame Format
• PPP is based on the High-Level Data Link
Control (HDLC) protocol
• The difference between PPP frames and HDLC
frames is that PPP frames contain protocol and
Link Control Protocol (LCP) fields
• LCP
– Described in RFCs 1548, 1570, 1661, 2153, and
2484
– Describes PPP organization and methodology,
including basic LCP extensions
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
8
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
9
Frame Format (continued)
• LCP field of the PPP packet can contain many
different pieces of information, including the
following:
–
–
–
–
–
–
–
Asynchronous character map
Maximum receive unit size
Compression
Authentication
Magic number
Link Quality Monitoring (LQM)
Multilink
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
10
Frame Format (continued)
• LCP link configuration process
– Modifies and enhances the default characteristics of
a PPP connection
• Includes the following actions:
–
–
–
–
–
Link establishment
Authentication (optional)
Link-quality determination (optional)
Network layer protocol configuration negotiation
Link termination
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
11
Establishing PPP Communications
• Involves the following actions:
– Link establishment
– Optional authentication
– Network layer protocol configuration negotiation
• The link establishment phase involves the
configuration and testing of the data link
• The authentication process can use two
authentication types with PPP connections: PAP
and CHAP
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
12
Establishing PPP Communications
(continued)
• PPP is an encapsulation type for serial interface
communications
– To configure a PPP connection, you must access the
interface configuration mode for the specific
interface you want to configure
• After LCP has finished negotiating the configuration
parameters
– Network layer protocols can be configured
individually by the appropriate NCP
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
13
Establishing PPP Communications
(continued)
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
14
Establishing PPP Communications
(continued)
• Configuring PPP Authentication
– Using authentication with PPP connections is
optional
– You must specifically configure PPP authentication
on each PPP host in order for the host to use it
– You can choose to enable CHAP, PAP, or both on
your PPP connection, in either order
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
15
Establishing PPP Communications
(continued)
• Once you set the authentication type
– You must still configure a username and password
for the authentication
• You must exit interface configuration mode and
enter global configuration mode
– Type username followed by the host name of the
remote router
– Then type password followed by the password for
that connection
• Confirming PPP Communications
– With the show interface command
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
16
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
17
Establishing PPP Communications
(continued)
CCNA Guide to Cisco Networking Fundamentals, Fourth Edition
18