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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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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)
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
LCP Configuration Options
The LCP configuration options are: Authentication Compression Error-detection Multilink PPP callback
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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)
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
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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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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.
Release 16/07/2009Jetking Infotrain Ltd.
Problem
The Business Development department still cannot have transaction with the other departments
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
Comparing HDLC and PPP - IIUsed 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)
Release 16/07/2009Jetking Infotrain Ltd.
Comparing HDLC and PPP - IIIProvides 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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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
Release 16/07/2009Jetking Infotrain Ltd.
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