CCNA CHAPTER 9 BY jetarvind kumar madhukar

Release 16/07/2009 Jetking Infotrain Ltd.
Establishing Serial Point-to-Point
Connection
Chapter 9

Release 16/07/2009Jetking Infotrain Ltd.
Chapter Objectives
 Explain wide area network
 Explain data-link protocols of point-to-point
leased lines
 Explain HDLC
 Explain PPP

Recall - I
 ACL are the statements, which are grouped together
by using a name or number
 ACLs supports the following types:
 Standard ACL
 Extended ACL
 You can use the access-list command to create an
ACL. The syntax to create an ACL is:
access-list ACL_# permit|deny conditions

Recall - II
 Wildcard masks can be used for matching a range
of IP addresses in ACL, instead of manually
entering it
 A wildcard is similar to an inverted subnet mask
 the extended ACL filters the source and destination
IP address, IP protocols such as IP, TCP, UDP ,
ICMP etc. and protocol information such as port
numbers or message types

Wide Area Network
 The terms and components of WAN are:
 Data Communications Equipment (DCE)
 Data Terminal Equipment (DTE)
 Customer Premises Equipment (CPE)
 Demarcation point
 Toll network
 Central Office (CO) switch
 Local loop

Wide Area Network (WAN)

Types of WAN
 WANs are available in four types, based on the
distance covered and the equipment used
 The four types of WAN are:
 Leased-Lines Connection
 Circuit-Switched Connection
 Packet-Switched Connections
 Cell-Switched Connections

Selecting WAN
 While connecting a LAN to a WAN, you should be
aware of the connection requirements
 Some of the major factors that help to select a WAN
are:
 Frequency
 Transfer rates
 Traffic load
 Cost

Data-Link Protocols
 Data-link layer protocols are commonly called the
data link protocols
 These protocols communicate between two devices
such as, routers, and bridges
 Data packets are sent over the link created by the
protocols
 Data-link protocols consist of:
 High Level Data Link Control (HDLC) protocol
 Point-to-Point protocol (PPP)

HDLC Frames

HDLC Frame Fields
Field Name Description
Flag Contains a single byte which indicates
the beginning or end of a frame
Address Contains the broadcast address which
is a binary sequence
Control Contains a single byte of binary
sequence. This calls for transmission
of user data in a non-sequence frame
Proprietary Contains information about the way to
carry multiple protocols on a single link
Data Contains encapsulated data. The
range if this field is variable
FCS Contains 2 to 4 bytes. Improves error
detection

Types of HDLC Frames

Configuring HDLC
 The encapsulation on a Cisco synchronous serial
interface is HDLC
 HDLC needs to be configured if the data link
protocol is change to some other protocol, and
HDLC has to be set back to default
 To configure the HDLC protocol to be set as default,
use the router CLI

Output of HDLC Verification

PPP
 The PPP allows computers to connect to the
Internet using a dial-up telephone line and ISDN
 PPP was originally designed to transport IP traffic
over point-to-point links
 PPP can transfer data over synchronous and
asynchronous links
 It supports a transfer of data over different network
protocols

PPP Frame
 The frame format of PPP is similar to the HDLC
Frame
 The only difference is that, PPP includes a Protocol
field
 The PPP frame is made up of six fields as shown in
Figure

PPP Stack

Link Control Protocol (LCP)
 The PPP Link Control Protocol can establish,
configure, maintain and terminate point-to-point
connection between the devices
 LCP uses following three classes of frames for
establishing, configuring, maintaining and
terminating connection between the devices:
 Link Configuration frames
 Link Maintenance frames
 Link Termination frames

Communication Between Devices

LCP Configuration Options
 The LCP configuration options are:
 Authentication
 Compression
 Error-detection
 Multilink
 PPP callback

PPP Session Establishment
 Point-to-Point protocol is used to transmit data
packets over serial point-to-point links
 The three phases of session establishment are
given as follows:
 Link establishment phase
 Authentication phase
 Network layer protocol phase

PPP Authentication - I
 Point-to-Point protocol supports authentication of
devices
 Once a link is established between nodes the
process of authentication starts
 PPP supports two authentication protocols
Password Authentication Protocol (PAP) and
Challenge Handshake Authentication Protocol
(CHAP)

PPP Authentication - II

CHAP Authentication

Configuring PPP
 Cisco allows you to configure the PPP to be used on
WAN interface
 You can configure the PPP using encapsulation and
interface commands in the configuration mode
 The syntax of the command to configure PPP is:
encapsulation ppp

Configuring PPP Authentication
 Once the serial interface is configured to support the
PPP encapsulation, you must configure PPP
authentication on the routers
 Before authentication process, it is required to set a
hostname for the router if not already assigned
 Also, you must set username and password for the
remote router to which the router is connected
 After the hostname, username and password is set ,
select the appropriate authentication for the router
such as PAP or CHAP

Verifying PPP Encapsulation
 PPP does not begin authentication until the Link
Control Protocol (LCP) process is completed and
open
 PPP authentication needs to be set up on both ends
for the authentication process to work
 Using commands, such as show and debug you can
solve problems for PPP

Mismatched WAN Encapsulations
 Routers can communicate in a network only if their
encapsulation methods are same
 If you connect two routers in the network using
point-to-point link but the encapsulation methods are
different on each router, the connection between the
routers is not established
 In this case, if one router sends request to the other,
it will never receive a response from that router

Mismatched IP Addresses
 Routers configured with same WAN encapsulation
method such as PPP, HDLC or Frame Relay
connected in different subnets will have connection
established between them
 However, the data packets do not transfer between
the routers. It becomes very difficult to identify this
problem, as the link appears to be functioning
properly
 To resolve the problem, you can use the show
running-config and show interface command on
each router

Case Study
The Blue Diamond steel company, Gujarat branch has
all Cisco routers connected in the network. The router
of the Business Development department is
damaged. The computers in this department cannot
exchange data with the other departments in the
network. The network administrator Robert replaces
the damaged router with a new non-Cisco router.

Problem
The Business Development department still cannot
have transaction with the other departments

Suggested Solution
Cisco routers by default use HDLC as the serial
encapsulation method on Cisco serial links. If you
connect a non-Cisco router to a Cisco router in the
network, data transfer does not occur between them.
To enable communication between the routers,
implement the Point-to-Point encapsulation method.
You must configure PPP on all the serial interfaces of
both the routers

Comparing HDLC and PPP - I
HDLC PPP
Fails to provide a method of detecting
errors
Uses FCS to detect errors while
transmitting data
Consist of two types; ISO HDLC and
Cisco HDLC
Based on ISO's HDLC frame format
Supports synchronous and
asynchronous links
Supports synchronous, asynchronous,
High-Speed Serial Interface (HSSI),
and ISDN links

Comparing HDLC and PPP - II
Used to perform encapsulation of data
without using other encapsulation
protocols
Used to transfer data. PPP cannot
encapsulate data without the help of
other encapsulation protocols, such
as, HDLC and Synchronous Data Link
Control (SDLC)
Fails to provide authentication
between two nodes or devices
Provides authentication using
protocols, such as, PPP Authentication
Protocol (PAP), and Challenge
Handshake Authentication Protocol
(CHAP)

Comparing HDLC and PPP - III
Provides a frame format that contains
a proprietary field. The other six fields
are similar to the PPP frame field.
Note, the ISO HDLC frame contains
only six fields, as the proprietary field
is not present
Provides a frame format that contains
a protocol field. The other six fields are
similar to the HDLC frame field
Fails to check for quality of a link
established
Uses Link Control Protocol (LCP) to
the check for quality of an established
link

Summary - I
 WAN is a network that spans a large geographical
area
 Leased lines are a transmission line, which is provided
by telephone companies to a particular customer
 Frequency, usage, traffic and cost are factors that
need to considered when selecting a WAN connection
 Data-Link layer protocols are commonly called the
data link protocols, which communicate between two
devices

Summary - II
 Configuring HDLC only needs to be done only if the data
link protocol is change to some other protocol
 The two types of HDLC:
 ISO HDLC
 Cisco HDLC
 The Cisco HDLC contains proprietary field, which
defines carrying a multiple protocols across a link
 PPP enables computers to connect to the internet using
a dial-up telephone line and ISDN
 Configuring the PPP is to specify that PPP is to be used
on the WAN

Summary - III
 Features of PPP are:
 Authentication
 Link test
 Error-detection
 Compression
 Components of PPP are:
 HDLC
 LCP
 NCPs
 Authentication protocols supported by PPP are:
 PAP
 CHAP

Summary - IV
 By default the authentication is not mandatory but
must be specified to
 PAP is a insecure protocol because the username
and password is sent in plain text
 Using CHAP protocol the server sends challenge
messages to the node. The node calculates and
sends the results back to the server

CCNA CHAPTER 9 BY jetarvind kumar madhukar

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CCNA CHAPTER 9 BY jetarvind kumar madhukar