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Transcript of Ppt in Chapter 16
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Troubleshooting WAN
Implementation Issues
Chapter 16
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Chapter Objectives
At the end of this Chapter you will be able to:Configure and verify a PPP connection between Cisco routersConfigure and verify Frame Relay on Cisco routers
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High-Level Data-Link Control (HDLC) Protocol
Introduction
The High-Level Data-Link Control (HDLC) protocol is a popular ISO-
standard, bit-oriented, Data Link layer protocol. It specifies an
encapsulation method for data on synchronous serial data links using
frame characters and checksums.
HDLC is a point-to-point protocol used on leased lines. No
authentication can be used with HDLC.
HDLC is the default encapsulation used by Cisco routers over
synchronous serial links. And Ciscos HDLC is proprietaryit wont
communicate with any other vendors HDLC implementation.
Figure below shows the Cisco HDLC format.
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Cisco HDLC format
Cisco HDLC Frame Format
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Point-to-Point Protocol (PPP)
When would you choose to use PPP?
Basic purpose of PPP is to transport layer 3 packets across a Data
Link layer point-to-point link,
its nonproprietary. So unless you have all Cisco routers, you needPPP on your serial interfacesthe HDLC encapsulation is Cisco
proprietary.
since PPP can encapsulate several layer 3 routed protocols and
provide authentication, dynamic addressing, and callback.
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PPP Authentication Methods
PPP Authentication MethodsThere are two methods of authentication that can be used with PPP
links:
Password Authentication Protocol (PAP)
The Password Authentication Protocol (PAP) is the less secure of
the two methods. Passwords are sent in clear text, and PAP is only
performed upon the initial link establishment. When the PPP link is
first established, the remote node sends the username and
password back to the originating router until authentication is
acknowledged.
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Conti..
Challenge Handshake Authentication Protocol (CHAP)
The Challenge Handshake Authentication Protocol (CHAP) is used
at the initial startup of a link and at periodic checkups on the link to
make sure the router is still communicating with the same host.
After PPP finishes its initial link-establishment phase, the local
router sends a challenge request to the remote device. The remote
device sends a value calculated using a one-way hash function
called MD5. The local router checks this hash value to make sure it
matches. If the values dont match, the link is immediately
terminated.
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Configuring PPP Encapsulation
Configuring PPP encapsulation on an interface is straightforward.
To configure it from the CLI, follow these simple router commands:
Router#config t
Router(config)#int s0
Router(config-if)#encapsulation ppp
Router(config-if)#^Z
Router#
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Configuring PPP Authentication
After you configure your serial interface to support PPP
encapsulation, you can configure authentication using PPP between
routers. First, you need to set the hostname of the router, if its not
already. Then you set the username and password for the remote
router that will be connecting to your router:
Router#config t
Router(config)#hostname RouterA
RouterA(config)#username RouterB password cisco
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Now, after youve set the hostname, usernames, and passwords,choose the authentication type, either CHAP or PAP:
RouterA#config t
Enter configuration commands, one per line. End with CNTL/Z.
RouterA(config)#int s0
RouterA(config-if)#ppp authentication chap pap
RouterA(config-if)#^Z
RouterA#
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Frame Relay
What is Frame Relay?
Frame Relay is still one of the most popular WAN services deployed
over the past decade, and theres a good reason for thiscost.
By default, Frame Relay is classified as a non-broadcast multi-
access (NBMA) network, meaning it doesnt send any broadcasts
like RIP updates across the network.
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Explaining Frame Relay Technology
Frame Relay is a packet-switched technology. You wont be using theencapsulation hdlc or encapsulation ppp command to configure it.
Frame Relay doesnt work like a point-to-point leased line.
Before Frame Relay
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Conti..
After Frame Relay
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Committed Information Rate (CIR)
CIR: The maximum bandwidth of data guaranteed to be delivered.In reality, its the average amount that the service provider will allow
you to transmit.
Heres an example: Lets say that you buy an access rate of T1
(1.544Mbps) and a CIR of 256Kbps. By doing this, the first 256Kbps
of traffic you send is guaranteed to be delivered. Anything beyond
that is called a burst a transmission that exceeds your
guaranteed 256Kbps rate, and can be any amount up to the T1
access rate (if that amount is in your contract). If your combined
committed burst (the basis for your CIR) and excess burst sizes,
known as the MBR or maximum burst rate
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Virtual Circuits
Permanent virtual circuits (PVCs) are by far the most common
type in use today. What permanent means here is that the telco
creates the mappings inside their gear and as long as you pay the
bill, theyll remain in place.
Switched virtual circuits (SVCs) are more like a phone call. The
virtual circuit is established when data needs to be transmitted, then
its taken down when the data transfer is complete.
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Data Link Connection Identifiers (DLCIs)
Frame Relay PVCs are identified to DTE end devices by Data LinkConnection Identifiers (DLCIs). A Frame Relay service provider
typically assigns DLCI values, which are used on Frame Relay
interfaces to distinguish between different virtual circuits. Because
many virtual circuits can be terminated on one multipoint Frame
Relay interface
DLCI on a local computer
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Conti..
RouterA(config-if)#frame-relay interface-dlci ? Define a DLCI as part of the current
RouterA(config-if)#frame-relay interface-dlci 16
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Local Management Interface (LMI)
Local Management Interface (LMI) is a signaling standard usedbetween your router and the first Frame Relay switch its connected
to. It allows for passing information about the operation and status of
the virtual circuit between the providers network and the DTE (your
router).
RouterA(config-if)#frame-relay lmi-type ?
cisco
ansi
q933a
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Frame Relay Implementation
RouterA#config t
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
RouterA#
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Configuring PPP with Authentication Using SDM
Create New Connection Wizard
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Conti..
Serial WAN Configuration Wizard
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Configure HDLC
Conti..
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IP Address Dialogue Box
Conti..
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Authentication Dialogue Box
Conti..
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Conti..
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Configuring Frame Relay with SDM
Configuration Encapsulation Wizard
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Configuring Static IP
Conti..
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Configure LMI & DLCI
Conti..
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Configuration Summary
Conti..
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THANK YOU