Transcript
Sybex CCNA 640-802 Chapter 14: Wide Area Networks
Instructor & Todd Lammle
Chapter 14 Objectives
The CCNA Topics Covered in this chapter include:
• Introduction to WAN’s• HDLC• PPP• Frame Relay• Introduction to VPN’s
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Defining WAN Terms
• Customer Premises Equipment (CPE)
• Demarcation (demarc)
• Local loop
• Central Office (CO)
• Toll network
WAN Connection Types
DTE-DCE-DTE
WAN Support
• Frame Relay
• ISDN
• LAPB
• LAPD
• HDLC
• PPP
• ATM
HDLC Protocol
• Bit-oriented Data Link layer ISO standard protocol
• Specifies a data encapsulation method
• No authentication can be used
HDLC Frame Format
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
Point-to-Point Protocol Stack
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
• Authentication– PAP– CHAP
• Compression– Stacker– Predictor
• Error detection– Quality– Magic Number
• Multilink– Splits the load for PPP over 2+ parallel
circuits; a bundle
PPP Session Establishment
• Link-establishment phase
• Authentication phase
• Network-layer protocol phase
PPP Session Establishment
PPP Authentication Methods
• Password Authentication Protocol (PAP)– Passwords sent in clear text– Remote node returns username &
password
• Challenge Authentication Protocol (CHAP)– Done at start-up & periodically– Challenge & Reply
• Remote router sends a one-way hash ~ MD5
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 remoteremote router
(2) Passwords must match
• Step #3: Choose Authentication type for each router; CHAP/PAPRouter__(Config)#int s0
Router__(config-if)#ppp authentication chap
Router__(config-if)#ppp authentication pap
Router__(config-if)#^Z
PPP Example 1
PPP Example 2
PPP Example 3
PPP Example 4
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
Before Frame Relay
After Frame Relay
Frame Relay
• Purpose– Provide a communications
interface between DTE & DCE equipment
– Connection-oriented Data Link layer communication
• Via virtual circuits• Provides a complete path from the
source to destination before sending the first frame
Frame Relay Terminology
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)
• 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
• Local Significance: – DLCIs do not need to be unique
• ConfigurationRouterA(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
DLCI’s are Locally Significant
Local Management Interface (LMI)
• Background
• Purpose
• LMI Messages– Keepalives– Multicasting– Multicast addressing– Status of virtual circuits
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– Inactive– Deleted
Sub-interfaces
• Definition– Multiple virtual circuits on a single
serial interface– 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
Partial Meshed Networks
Creating Sub-interfaces
Configuration:#1: Set the encapsulation on the serial interface
#2: Define the subinterfaceRouterA(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
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
RouterA(config)#int s0
RouterA(config-if)#encap frame
RouterA(config-if)#int s0.16 point-to-point
RouterA(config-if)#no inverse-arp
RouterA(config-if)#ip address 172.16.30.1 255.255.255.0
RouterA(config-if)#frame-relay map ip 172.16.30.17 16 ietf broadcast
RouterA(config-if)#frame-relay map ip 172.16.30.18 17 broadcast
RouterA(config-if)#frame-relay map ip 172.16.30.19 18
Using the inverse arp command
RouterA(config)#int s0.16 point-to-point
RouterA(config-if)#encap frame-relay ietf
RouterA(config-if)#ip address 172.16.30.1 255.255.255.0
Congestion Control
• Discard Eligibility (DE)
• Forward-Explicit Congestion Notification (FECN)
• Backward-Explicit Congestion Notification (BECN)
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
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
Why can’t RouterA talk to RouterB?Why can’t RouterA talk to RouterB?
Troubleshooting Frame Relay
Why is RIP not sent across the PVC?Why is RIP not sent across the PVC?
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
• REMOTE ACCESS VPNSRemote access VPNs allow remote users like telecommuters to securely
access the corporate network wherever and whenever they need to.
• SITE-TO-SITE VPNSSite-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 VPNSExtranet 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
– Open your books and go through all the written labs and the review questions.
– Review the answers in class.
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