Transcript Chapter16

Sybex CCNA 640-802
Chapter 16: 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
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Customer Premises Equipment (CPE)
Demarcation (demarc)
Local loop
Central Office (CO)
Toll network
WAN Connection Bandwidth
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Digital Signal 0 (DS0) This is the basic digital signaling rate of 64Kbps,
equivalent to one channel. Europe uses the E0 and Japan uses the J0 to
reference the same channel speed. Typically used in a T-carrier
transmission, this is the generic term used by several multiplexed digital
carrier systems. This is the smallest capacity digital circuit. 1 DS0 = 1
voice/data line.
T1 Also referred to as a DS1, this contains 24 DS0 circuits bundled
together with a total bandwidth of 1.544Mbps.
E1 European equivalent of the T1. Contains 30 DS0 circuits bundled
together with a bandwidth of 2.048Mbps.
T3 Referred to as a DS3, this has 28 DS1s bundled together, or 672
DS0s, with a bandwidth of 44.736Mbps.
OC-3 Optical Carrier (OC) 3, uses fiber, is made up of three DS3s
bundled together, and contains 2,016 DS0s with a total bandwidth of
155.52Mbps.
OC-12 Optical Carrier 12 is make up of four OC-3s bundled together and
contains 8,064 DS0s with a total bandwidth of 622.08Mbps.
OC-48 Optical Carrier 48 is made up of four OC12s bundled together
and contains 32,256 DS0s with a total bandwidth of 2488.32Mbps.
WAN Connection Types
WAN Support
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Frame Relay
ISDN
LAPB
LAPD
HDLC
PPP
ATM
PPPoE
Cable
DSL
MPLS
DWDM
Cable and DSL
Comparisons
– Speed
– Security
– Popularity
– Customer satisfaction
Cable Terms
• Headend
• Distribution network
• DOCSIS (Data Over Cable Service
Interface Specification)
Digital Subscriber Line (DSL)
• Symmetrical DSL
• Asymmetrical DSL
ADSL
• PPPoE
• RFC1483 Routing
• PPPoA
PPPoE with ADSL
DTE-DCE-DTE
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
on Router A to talk to Router B
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Step #1: Configure PPP
RouterA#config t
RouterA(config)#int s0
RouterAconfig-if)#encapsulation ppp
RouterA(config-if)#^Z
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Step #2: Define the username & password
RouterA(config)#username RouterB password
cisco
RouterB(config)#username RouterA password
cisco
NOTE: (1) Username maps to the remote router
(2) Passwords must match
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Step #3: Choose Authentication type for each router;
CHAP/PAP
RouterA(Config)#int s0
RouterA(config-if)#ppp authentication chap
RouterA(config-if)#ppp authentication pap
RouterA(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
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
Before Frame Relay
After Frame Relay
Frame Relay Terminology
• Committed Information Rate (CIR)
• Access rate
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
Frame Relay Encapsulation
• Specified on serial interfaces
• Encapsulation types:
– Cisco (default encapsulation type)
– IETF (used between Cisco & nonCisco 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
• 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
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
Congestion Control
• Discard Eligibility (DE)
• Forward-Explicit Congestion
Notification (FECN)
• Backward-Explicit Congestion
Notification (BECN)
Frame Relay Implementation
Single Interface
Partial Meshed Networks
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
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
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
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?
Troubleshooting Frame Relay
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 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-tobusiness (B2B) communications.
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Cisco IOS IPsec
• IPSec Transforms
specify a single security protocol with its
corresponding security algorithm
• Security Protocols
– Authentication Header (AH)
– Encapsulating Security
Payload (ESP)
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IpSec benefits
• Confidentiality
• Data origin authentication
and connectionless integrity
• Anti-replay service
• Traffic flow
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Encryption
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Symmetric encryption
Asymmetric Encryption
Private keys
Public keys
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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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