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Instructor & Todd Lammle. Sybex CCNA 640-802 Chapter 14: Wide Area Networks. Chapter 14 Objectives. The CCNA Topics Covered in this chapter include: Introduction to WAN’s HDLC PPP Frame Relay Introduction to VPN’s. 2. Defining WAN Terms. Customer Premises Equipment (CPE)

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Instructor todd lammle

Instructor & Todd Lammle

Sybex CCNA 640-802

Chapter 14: Wide Area Networks


Chapter 14 objectives
Chapter 14 Objectives

The CCNA Topics Covered in this chapter include:

  • Introduction to WAN’s

  • HDLC

  • PPP

  • Frame Relay

  • Introduction to VPN’s

2


Defining wan terms
Defining WAN Terms

  • Customer Premises Equipment (CPE)

  • Demarcation (demarc)

  • Local loop

  • Central Office (CO)

  • Toll network



Dte dce dte
DTE-DCE-DTE

Channel Service Unit (CSU) is a device that converts a digital data

frame from the communications technology used on a local area

network (LAN) into a frame appropriate to a wide-area network (WAN)

and vice versa.

The Data Service Unit (DSU) is a device that performs protective

and diagnostic functions for a telecommunications line.


Wan support
WAN Support

  • Frame Relay

  • ISDN: Integrated Services Digital Network

  • LAPB: Link Access Procedure, Balanced

  • LAPD: Link Access Procedure, D-channel

  • HDLC: High-level Data Link Control

  • PPP

  • ATM: Asynchronous Transfer Mode


Hdlc protocol
HDLC Protocol

  • Bit-oriented Data Link layer ISO standard protocol, i.e., control information is encoded by bits

  • Specifies a data encapsulation method on synchronous serial data links

  • A point-to point protocol used on leased lines

  • No authentication can be used



Point to point protocol ppp
Point-to-Point Protocol (PPP)

  • Purpose:

    • Transport layer-3 packets across a Data Link layer point-to-point link

  • Can be used over asynchronous serial (dial-up) or synchronous serial (ISDN) media

    • Uses Link Control Protocol (LCP)

      • Builds & maintains data-link connections



Ppp main components
PPP Main Components

  • EIA/TIA-232-C

    • Intl. Std. for serial communications

  • HDLC

    • Serial link datagram encapsulation method

  • LCP

    • Used in P-t-P connections:

      • Establishing

      • Maintaining

      • Terminating

  • NCP

    • Method of establishing & configuring Network Layer protocols

    • Allows simultaneous use of multiple Network layer protocols


Lcp configuration options
LCP Configuration Options

  • Authentication

    • PAP: Password Authentication Protocol

    • CHAP: Challenge Handshake Authentication Protocol

  • Compression

    • Stacker

    • Predictor

  • Error detection

    • Quality

    • Magic Number

  • Multilink

    • Splits the load for PPP over 2+ parallel circuits; a bundle


Ppp session establishment
PPP Session Establishment

  • Link-establishment phase

  • Authentication phase

  • Network-layer protocol phase



Ppp authentication methods
PPP Authentication Methods

  • Password Authentication Protocol (PAP)

    • Passwords sent in clear text

    • Remote node returns username & password

    • Only performed in initial link establishment

  • Challenge Handshake Authentication Protocol (CHAP)

    • Done at start-up & periodically

    • Challenge & Reply

      • Remote router sends a one-way hash ~ MD5


Configuring ppp
Configuring PPP

  • Step #1: Configure PPP on RouterA & RouterB:

    Router__#config t

    Router__(config)#int s0

    Router__(config-if)#encapsulation ppp

    Router__(config-if)#^Z

  • Step #2: Define the username & password on each router:

    • RouterA: RouterA(config)#username RouterB password cisco

    • RouterB: RouterB(config)#username RouterA password cisco

      NOTE: (1) Username maps to the remote router

      (2) Passwords must match

  • Step #3: Choose Authentication type for each router; CHAP/PAP

    Router__(Config)#int s0

    Router__(config-if)#ppp authentication chap

    Router__(config-if)#ppp authentication pap

    Router__(config-if)#^Z



Ppp example 2 failed ppp authentication
PPP Example 2: Failed PPP authentication


Ppp example 3 mismatched wan encapsulations
PPP Example 3:Mismatched WAN Encapsulations


Ppp example 4 mismatched ip address
PPP Example 4:Mismatched IP Address


Frame relay
Frame Relay

  • Background

    • High-performance WAN encapsulation method

    • OSI Physical & data Link layer

    • Originally designed for use across ISDN

  • Supported Protocols

    • IP, DECnet, AppleTalk, Xerox Network Service (XNS), Novell IPX, Banyan Vines, Transparent Bridging, & ISO




Frame relay1
Frame Relay

  • Purpose

    • Provide a communication interface between DTE & DCE equipments

    • Connection-oriented Data Link layer communication

      • Via virtual circuits: PVC, SVC

      • Provides a complete path from the source to destination before sending the first frame



Frame relay encapsulation
Frame Relay Encapsulation

  • Specified on serial interfaces

  • Encapsulation types:

    • Cisco (default encapsulation type)

    • IETF (used between Cisco & non-Cisco devices)

      RouterA(config)#int s0

      RouterA(config-if)#encapsulation frame-relay ?

      ietf Use RFC1490 encapsulation

      <cr>


Data link connection identifiers dlcis
Data Link Connection Identifiers (DLCIs)

  • Frame Relay PVCs are identified by DLCIs

  • IP end devices are mapped to DLCIs

    • Mapped dynamically or mapped by IARP

  • Global Significance:

    • Advertised to all remote sites as the same PVC, need LMI extensions

  • Local Significance:

    • DLCIs do not need to be unique

  • Configuration

    RouterA(config-if)#frame-relay interface-dlci ?

    <16-1007> Define a DLCI as part of the current

    subinterface

    RouterA(config-if)#frame-relay interface-dlci 16



Local management interface lmi
Local Management Interface (LMI)

  • Background: a signaling standard between a router and the first connected frame relay switch

  • Purpose: passing information about the operation and status of the VC between the DTE and switch

  • LMI Messages

    • Keepalives

    • Multicasting

    • Global addressing

    • Status of virtual circuits


Lmi types
LMI Types

  • Configuration:

    RouterA(config-if)#frame-relay lmi-type ?

    cisco

    ansi

    q933a

    • Beginning with IOS ver 11.2+ the LMI type is auto-sensed

    • Default type: cisco

  • Virtual circuit status:

    • Active: everything is up, routers can exchange information

    • Inactive: router interface is up and connected with the switch, but the remote router is not up

    • Deleted: no LMI info is being received on the interface from the switch


Single interfaces
Single interfaces

RouterA(config)#int s0/0

RouterA(config-if)#encapsulation frame-relay

RouterA(config-if)#ip address 172.16.20.1 255.255.255.0

RouterA(config-if)#frame-relay lmi-type ansi

RouterA(config-if)#frame-relay interface-dlci 101

RouterA(config-if)#^Z


Sub interfaces
Sub-interfaces

  • Definition

    • Multiple virtual circuits on a single serial interface: multiplexing

    • Enables the assignment of different network-layer characteristics to each sub-interface

      • IP routing on one sub-interface

      • IPX routing on another

    • Mitigates difficulties associated with:

      • Partial meshed Frame Relay networks

      • Split Horizon protocols


Creating sub interfaces
Creating Sub-interfaces

Configuration:

#1: Set the encapsulation on the serial interface

#2: Define the subinterface

RouterA(config)#int s0

RouterA(config)#encapsulation frame-relay

RouterA(config)#int s0.?

<0-4294967295> Serial interface number

RouterA(config)#int s0.16 ?

multipoint Treat as a multipoint link

point-to-point Treat as a point-to-point link


Sub interfaces1
Sub-interfaces

Point-to-point: a single virtual circuit connects one router to another. Each p-t-p subinterface requires its own subnet.

Multipoint: when the router is the center of a star of virtual circuits that are using a single subnet for all routers’ serial interfaces connected to the switch.


Mapping frame relay
Mapping Frame Relay

Necessary to IP end devices to communicate

  • Addresses must be mapped to the DLCIs

  • Methods:

    • Frame Relay map command

    • Inverse-arp function


Using the map command
Using the map command

RouterA(config)#int s0

RouterA(config-if)#encap frame

RouterA(config-if)#int s0.16 point-to-point

RouterA(config-subif)#no inverse-arp

RouterA(config-subif)#ip address 172.16.30.1 255.255.255.0

RouterA(config-subif)#frame-relay map ip 172.16.30.17 16 ietf broadcast


Using the inverse arp command
Using the inverse arp command

RouterA(config)#int s0.16 point-to-point

RouterA(config-subif)#encap frame-relay ietf

RouterA(config-subif)#ip address 172.16.30.1 255.255.255.0

RouterA(config-subif)#frame-relay interface-dlci 200


Committed information rate cir
Committed Information Rate (CIR)

  • Definition: Provision allowing customers to purchase amounts of bandwidth lower than what they might need

    • Cost savings

    • Good for bursty traffic

    • Not good for constant amounts of data transmission


Congestion control
Congestion Control

  • Discard Eligibility (DE):

    • Transmit packets beyond the CIR, the packets exceeding the CIR are to be discarded if network is congested at that time. These excessive bits are marked with a DE bit.

  • Forward-Explicit Congestion Notification (FECN)

    • When the frame relay network recognizes congestion in the cloud, the FECN bit will be set to 1 to notify the destination DTE that the path the frame just traversed is congested.

  • Backward-Explicit Congestion Notification (BECN)

    • When the switch detects congestions, it’ll set the BECN bit in a frame that’s destined for the source router.


Monitoring frame relay
Monitoring Frame Relay

RouterA>sho frame ?

ip show frame relay IP statistics

lmi show frame relay lmi statistics

map Frame-Relay map table

pvc show frame relay pvc statistics

route show frame relay route

traffic Frame-Relay protocol statistics

RouterA#sho int s0

RouterB#show frame map

Router#debug frame-relay lmi


Troubleshooting frame relay
Troubleshooting Frame Relay

Why can’t RouterA talk to RouterB?

You need to use your own DLCI number 100 instead of the remote

DLCI number to communicate with the switch.


Troubleshooting frame relay1
Troubleshooting Frame Relay

Why is RIP not sent across the PVC?

Because frame relay is a non-broadcast multi-access network, i.e., no

broadcast across the PVC. So it’s necessary to add broadcast in the

mapping statement.


Introduction to vpn s
Introduction to VPN’s

  • VPNs are used daily to give remote users and disjointed networks connectivity over a public medium like the Internet instead of using more expensive permanent means.

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Types of vpn s
Types of VPN’s

  • REMOTE ACCESS VPNS

    Remote access VPNs allow remote users like telecommuters to securely access the corporate network wherever and whenever they need to.

  • SITE-TO-SITE VPNS

    Site-to-site VPNs, or, intranet VPNs, allow a company to connect its remote sites to the corporate backbone securely over a public medium like the Internet instead of requiring more expensive WAN connections like Frame Relay.

  • EXTRANET VPNS

    Extranet VPNs allow an organization’s suppliers, partners, and customers to be connected to the corporate network in a limited way for business-to-business (B2B) communications.

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Written labs and review questions
Written Labs and Review Questions

  • Open your books and go through all the written labs and the review questions.

  • Review the answers in class.

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