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TRANSCRIPT
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Establishing Frame Relay Connection
Chapter 11
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Chapter 11 2
Chapter Objectives
Discuss the Frame Relay componentsExplain virtual circuit Explain LMI configuration and EncapsulationExplain DLCI addressing detailsExplain concerns of network layer and frame layer
Troubleshoot LMI Configure Frame Relay
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Chapter 11 3
Recall - I
S peed, Multiple Device S upport, Inexpensive areThe features of I S DN areNetwork Termination Device 1 (NT1), NetworkTermination Device 2 (NT2), I S DN Router, TerminalEquipment 1 (TE1), Terminal Equipment 2 (TE2),Terminal Adapter (TA) are e I S DN devicesIS DN is a channelized service. A channelizedservice splits a wire into many logical channels or time slots
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Chapter 11 4
Recall - II
IS DN supports two types of connections such as theBasic Rate Interface (BRI) and Primary RateInterface (PRI)You can verify the I S DN connections using twocommands:
show interface commandshow isdn status command
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Chapter 11 5
Frame Relay
F eatures of F rame RelayOperates at a higher speed (44.3 Mbps)Operates only in physical and data link layers
Is less expensive than other WAN connectionsuch as X.25Has error detection at the data link layer onlyProvides faster transmission for media that are
more reliable and protocols that have flow anderror control at the higher layers
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Frame Relay Components - I
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Chapter 11 7
Frame Relay Components - II
The basic terms associated with the F rame Relaynetwork are as follows:
Data Terminal Equipment (DTE)
Data Communications Equipment (DCE)Access linkLocal access rateDLCI
LMICommitted Information (CIR)
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Frame Relay Components - III
Committed burst (Bc)Excess Burst (Be)F orward explicit congestion notification ( F ECN)
Backward explicit congestion notification (BECN)Discard Eligibility (DE) indicator
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Logical Connectivity of Frame Relay
Network
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Committed Information Rate (CIR)
F rame Relay allows multiple users to use the packetswitched network at the same timeThe only limitation of F rame Relay is that not allusers can transmit the data at the same timeF rame Relay provides dedicated bandwidths to allthe users for data transmissionThe F rame Relay can function as a leased line if the
access rate and CIR values are same
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Chapter 11 11
Standard Frame Relay Frame Structure
The frame format allows you to understand thefunctionality of F rame RelayEach frame has flags that indicate the start and end
of the frame
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Frame Relay Encapsulation Types
The F rame Relay has two types of encapsulationsthat you can view using the encapsulation frame-relay ? command:
CiscoInternet Engineering Task F orce (IET F )
The devices in a network can communicate only if their F rame Relay encapsulation types are same
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Virtual Circuit
A Virtual Circuit (VC) represents the path on whichthe frame travels. Virtual circuits enable you tocompare F rame Relay to leased physical circuitThere are two types of virtual circuits, such as:
Permanent Virtual Circuit (PVC)S witched Virtual Circuit ( S VC)
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Virtual Circuits
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Partial Mesh Network
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LMI Configuration and Encapsulation
LMI is the signaling standard used between theF rame Relay DTE and F rame Relay DCELMI is the communication between the router andthe nearest F rame Relay switchThe LMI performs the following functions:
Implements a keepalive function to verify the flowof data between the DTE and DCE
Informs whether Permanent Virtual Circuit (PVC)is active or not
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LAPF Header
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Identifying the type of protocol
If the F rame Relay is using the LAP F header thenthe DTEs cannot support multiprotocol trafficbecause there is no way to identify the type of protocolTo solve this problem. Cisco Encapsulation andRF C 1490 Encapsulation is used
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Cisco Encapsulation
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RFC 1490 Encapsulation
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DLCI Addressing
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DLCI Addressing Details
The exact number of DLCI is dependent on thefollowing factors:
Protocols being routed
Broadcast trafficS peed of lineS tatic RoutesS ize of routing protocol and S AP updates
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F rame Relay involves following issues related to thetransmission of data packets from the layer 3 across
the network:Layer 3 addressing with F rame RelayBroadcast handling
Concerns of Network Layer and
Frame Relay
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Frame Relay Layer 3 Addressing
The F rame Relay implementation of Cisco providesthree different options to assign subnets and IPaddress on the F rame Relay interfaces. The optionsare:
A subnet that contains all the F rame Relay DataTerminal Equipments (DTE)A subnet for each virtual circuitHybrid of the above two options
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Full Mesh Network
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Partial Mesh Network
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Hybrid Network
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Broadcast Handling
The F rame Relay can send copies of broadcast over all the virtual circuitsThe F rame Relay does not have the capability toreplicate and deliver across multiple virtual circuitsto several destinationsThe routers need to send broadcast for certainfeatures to activate their functioning
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Frame Relay Service Internetworking
F rame Relay networks use Asynchronous Transfer Mode (ATM) in the core of the F rame Relay networkThe working of ATM is similar to a F rame Relay.However, ATM has certain features that make itmore effective than F rame RelayThe service provider uses the ATM to build the coreof the F rame Relay networks as shown in figure
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Frame Relay Network
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Network as it Appears to Routers
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Configuration Steps for Remote
Router routes
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Steps to Change DLCI Status
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Frame Configuration Command - I
Commands Description
encapsulation frame-relay[ieft|cisco]
Defines the F rame Relayencapsulation which is preferred over HDLC and PPP
frame-relay lmi-type{ansi|q933a|cisco]
Defines the type of LMI messages thatare sent to the switch
bandwidth num Enables to set the interface speed of the router
frame-relay map [protocolprotocol-addressdlci}payload-compressionfrf9 stac caim [element-number][broadcast][ieft|cisco]
Defines statically the mappingbetween the network layer and DLCI
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Frame Configuration Command - II
k eepalive sec Enables to configure the way and timeinterval that the LMI messages aresent and received
interface serial number.sub
[point-to-point|multipoint]Enables to create a subinterface or reference a subinterface that isalready created
frame-relay interface-dlcidlci [ieft|cisco] [voice-circir] [ppp virtual-template-
name]
Links the DLCI to the subinterface
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Frame Configuration Commands in
the Privileged Mode - ICommand Description
show interfaces Displays the status of the physicalinterface
show frame-relay lmi [typenumber]
Displays LMI status information
show frame-relay pvc Displays a list of all the configuredPVCs and DLCI numbers
show frame-relay map Provides a list of network layer
addresses mapped to DLCI numbersshow ip route Displays the available routes for the
packets to travel from one router toanother
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Basic Frame Relay Network
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Verification of Frame Relay
Encapsulation on Router1
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Output of show ip route Command
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Output of show frame-relay lmi
Command
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Output of show frame-relay pvc
Command
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Output of show frame-relay map
Command
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Chapter 11 43
Configuring Frame Relay
SubinterfacesF rame Relay subinterfaces provide a solution to theproblem of split horizon on the partially meshedF rame Relay networksCisco routers support two types of subinterfacesgiven as follows:
Point-to-point subinterface
Multipoint subinterfaces
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Frame Relay Point-to-Point
Subinterfaces
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Output of show frame-relay lmi
Command
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Chapter 11 46
Output of show frame-relay pvc
Command
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Output of show frame-relay map
Command
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Frame Relay Multipoint Subinterfaces
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Output of show frame-relay lmi
Command
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Output of show frame-relay pvc
Command
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Output of show frame-relay map
Command
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Hub-and-Spoke Frame Relay Network
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Output of show frame-relay lmi
Command
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Output of show frame-relay pvc
Command
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Output of show frame-relay map
Command
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Fully Meshed Network
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Output of show frame-relay lmi
Command
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Output of show frame-relay pvc
Command
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Output of show frame-relay map
Command
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Frame Relay Congestion Control
F rame Relay reduces the network overhead byimplementing congestion-control mechanismF rame Relay implements two congestion-notificationmechanisms such as F orward-explicit congestion
notification ( F ECN) and Backward-explicit congestionnotification (BECN)The F rame Relay frame includes following three bitsthat allow congestion control:
Discard Eligibility (DE)F orward-explicit congestion notification ( F ECN)Backward-explicit congestion notification (BECN)
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Chapter 1161
Frame Relay Error Checking
F rame Relay uses cyclic redundancy check (CRC)error checking mechanismThe CRC compares two derived values from the twomathematical functions computed at the source andthe destination devicesThis determines whether an error occurred duringthe transmission of data from source to destination
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Chapter 1162
Case Study
At the Gujarat branch of the Blue Diamond S teelorganization, all Cisco routers are implemented on thenetwork. The routers use HDLC as the defaultencapsulation method for data transmission. All the
transaction between the departments of the companyis carried out over the network. However,unfortunately, some important information of F inancedepartment regarding policies could not reach to the
S oftware Management departments destinationcomputer because it was lost in transit.
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Chapter 1163
Problem
Information was lost due to network congestion
in network
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Chapter 1164
Suggested Solution
All the branches should be integrated using theF rame Relay technology. F rame Relay provides a
congestion control mechanism that can prevent theloss of critical data
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Chapter 1165
Frame Relay Backup using ISDN
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Chapter 1166
Output of show frame-relay lmi
Command
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Chapter 1167
Output of show frame-relay pvc
Command
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Chapter 1168
Output of show frame-relay map
Command
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Chapter 1169
Output of show ip route Command
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Chapter 1170
Troubleshooting Frame Relay
The commons issues in the F rame Relay can beresolved using the debug commandThis command enables you to troubleshoot theF rame Relay connectionsYou can use the router console to enter thesecommands:
debug frame-relay events Commanddebug F rame Relay packet Command
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Chapter 1171
Summary - I
F rame Relay networks are multi-access networks wheremore than two devices can be attached to the networkA Virtual circuit (VC) represents the path on which theframe travels. Virtual circuits enable you to compareF rame Relay to leased physical circuit. There two typesof virtual circuits are:
Permanent virtual circuit (PVC)S witched virtual circuit ( S VC)
LMI is the definition used between the F rame Relay DTEand F rame Relay DCE, which means that the data sendby the DTE is processed between them
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Chapter 1172
Summary - II
S ometimes you might face problems with theconnection to the carrier switch. The commandsavailable are to troubleshoot LMI are:
show interfacesshow frame-relay lmidebug frame-relay lmi
The DLCI identifies a virtual circuit for the F rame
Relay to forward the frames to appropriate remotesite when multiple access list use the same accesslist
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Summary - III
The F rame Relay implementation of Cisco provideswith three different options to assign subnets and IPaddress on the F rame Relay interfaces. The optionsare:
A subnet that contains all the F rame Relay dataterminal equipments (DTE)A subnet for each virtual circuit
Hybrid of the above twoF rame Relay networks use Asynchronous Transfer Mode (ATM) in the core of the F rame Relay network