CCNA CHAPTER 11 BY jetarvind kumar madhukar

Release 16/07/2009 Jetking Infotrain Ltd.
Establishing Frame Relay
Connection
Chapter 11

Release 16/07/2009Jetking Infotrain Ltd.
Chapter Objectives
 Discuss the Frame Relay components
 Explain virtual circuit
 Explain LMI configuration and Encapsulation
 Explain DLCI addressing details
 Explain concerns of network layer and frame layer
 Troubleshoot LMI
 Configure Frame Relay

Recall - I
 Speed, Multiple Device Support, Inexpensive are
The features of ISDN are
 Network Termination Device 1 (NT1), Network
Termination Device 2 (NT2), ISDN Router, Terminal
Equipment 1 (TE1), Terminal Equipment 2 (TE2),
Terminal Adapter (TA) are e ISDN devices
 ISDN is a channelized service. A channelized
service splits a wire into many logical channels or
time slots

Recall - II
 ISDN supports two types of connections such as the
Basic Rate Interface (BRI) and Primary Rate
Interface (PRI)
 You can verify the ISDN connections using two
commands:
 show interface command
 show isdn status command

Frame Relay
 Features of Frame Relay
 Operates at a higher speed (44.3 Mbps)
 Operates only in physical and data link layers
 Is less expensive than other WAN connection
such as X.25
 Has error detection at the data link layer only
 Provides faster transmission for media that are
more reliable and protocols that have flow and
error control at the higher layers

Frame Relay Components - I

Frame Relay Components - II
 The basic terms associated with the Frame Relay
network are as follows:
 Data Terminal Equipment (DTE)
 Data Communications Equipment (DCE)
 Access link
 Local access rate
 DLCI
 LMI
 Committed Information (CIR)

Frame Relay Components - III
 Committed burst (Bc)
 Excess Burst (Be)
 Forward explicit congestion notification (FECN)
 Backward explicit congestion notification (BECN)
 Discard Eligibility (DE) indicator

Logical Connectivity of Frame Relay
Network

Committed Information Rate (CIR)
 Frame Relay allows multiple users to use the packet
switched network at the same time
 The only limitation of Frame Relay is that not all
users can transmit the data at the same time
 Frame Relay provides dedicated bandwidths to all
the users for data transmission
 The Frame Relay can function as a leased line if the
access rate and CIR values are same

Standard Frame Relay Frame Structure
 The frame format allows you to understand the
functionality of Frame Relay
 Each frame has flags that indicate the start and end
of the frame

Frame Relay Encapsulation Types
 The Frame Relay has two types of encapsulations
that you can view using the encapsulation frame-
relay ? command:
 Cisco
 Internet Engineering Task Force (IETF)
 The devices in a network can communicate only if
their Frame Relay encapsulation types are same

Virtual Circuit
 A Virtual Circuit (VC) represents the path on which
the frame travels. Virtual circuits enable you to
compare Frame Relay to leased physical circuit
 There are two types of virtual circuits, such as:
 Permanent Virtual Circuit (PVC)
 Switched Virtual Circuit (SVC)

Virtual Circuits

Partial Mesh Network

LMI Configuration and Encapsulation
 LMI is the signaling standard used between the
Frame Relay DTE and Frame Relay DCE
 LMI is the communication between the router and
the nearest Frame Relay switch
 The LMI performs the following functions:
 Implements a keepalive function to verify the flow
of data between the DTE and DCE
 Informs whether Permanent Virtual Circuit (PVC)
is active or not

LAPF Header

Identifying the type of protocol
 If the Frame Relay is using the LAPF header then
the DTEs cannot support multiprotocol traffic
because there is no way to identify the type of
protocol
 To solve this problem. Cisco Encapsulation and
RFC 1490 Encapsulation is used

Cisco Encapsulation

RFC 1490 Encapsulation

DLCI Addressing

DLCI Addressing Details
 The exact number of DLCI is dependent on the
following factors:
 Protocols being routed
 Broadcast traffic
 Speed of line
 Static Routes
 Size of routing protocol and SAP updates

 Frame Relay involves following issues related to the
transmission of data packets from the layer 3 across
the network:
 Layer 3 addressing with Frame Relay
 Broadcast handling
Concerns of Network Layer and
Frame Relay

Frame Relay Layer 3 Addressing
 The Frame Relay implementation of Cisco provides
three different options to assign subnets and IP
address on the Frame Relay interfaces. The options
are:
 A subnet that contains all the Frame Relay Data
Terminal Equipments (DTE)
 A subnet for each virtual circuit
 Hybrid of the above two options

Full Mesh Network

Hybrid Network

Broadcast Handling
 The Frame Relay can send copies of broadcast over
all the virtual circuits
 The Frame Relay does not have the capability to
replicate and deliver across multiple virtual circuits
to several destinations
 The routers need to send broadcast for certain
features to activate their functioning

Frame Relay Service Internetworking
 Frame Relay networks use Asynchronous Transfer
Mode (ATM) in the core of the Frame Relay network
 The working of ATM is similar to a Frame Relay.
However, ATM has certain features that make it
more effective than Frame Relay
 The service provider uses the ATM to build the core
of the Frame Relay networks as shown in figure

Frame Relay Network

Network as it Appears to Routers

Configuration Steps for Remote
Router routes

Steps to Change DLCI Status

Frame Configuration Command - I
Commands Description
encapsulation frame-relay
[ieft|cisco]
Defines the Frame Relay
encapsulation which is preferred over
HDLC and PPP
frame-relay lmi-type{ansi|
q933a|cisco]
Defines the type of LMI messages that
are sent to the switch
bandwidth num Enables to set the interface speed of
the router
frame-relay map [protocol
protocol-address
dlci}payload-compression
frf9 stac caim [element-
number][broadcast] [ieft|
cisco]
Defines statically the mapping
between the network layer and DLCI

Frame Configuration Command - II
keepalive sec Enables to configure the way and time
interval that the LMI messages are
sent and received
interface serial number.sub
[point-to-point|multipoint]
Enables to create a subinterface or
reference a subinterface that is
already created
frame-relay interface-dlci
dlci [ieft|cisco] [voice-cir
cir] [ppp virtual-template-
name]
Links the DLCI to the subinterface

Frame Configuration Commands in
the Privileged Mode - I
Command Description
show interfaces Displays the status of the physical
interface
show frame-relay lmi [type
number]
Displays LMI status information
show frame-relay pvc Displays a list of all the configured
PVCs and DLCI numbers
show frame-relay map Provides a list of network layer
addresses mapped to DLCI numbers
show ip route Displays the available routes for the
packets to travel from one router to
another

Basic Frame Relay Network

Verification of Frame Relay
Encapsulation on Router1

Output of show ip route Command

Output of show frame-relay lmi
Command

Output of show frame-relay pvc
Command

Output of show frame-relay map
Command

Configuring Frame Relay
Subinterfaces
 Frame Relay subinterfaces provide a solution to the
problem of split horizon on the partially meshed
Frame Relay networks
 Cisco routers support two types of subinterfaces
given as follows:
 Point-to-point subinterface
 Multipoint subinterfaces

Frame Relay Point-to-Point
Subinterfaces

Frame Relay Multipoint Subinterfaces

Hub-and-Spoke Frame Relay Network

Fully Meshed Network

Frame Relay Congestion Control
 Frame Relay reduces the network overhead by
implementing congestion-control mechanism
 Frame Relay implements two congestion-notification
mechanisms such as Forward-explicit congestion
notification (FECN) and Backward-explicit congestion
notification (BECN)
 The Frame Relay frame includes following three bits
that allow congestion control:
 Discard Eligibility (DE)
 Forward-explicit congestion notification (FECN)
 Backward-explicit congestion notification (BECN)

Frame Relay Error Checking
 Frame Relay uses cyclic redundancy check (CRC)
error checking mechanism
 The CRC compares two derived values from the two
mathematical functions computed at the source and
the destination devices
 This determines whether an error occurred during
the transmission of data from source to destination

Case Study
At the Gujarat branch of the Blue Diamond Steel
organization, all Cisco routers are implemented on the
network. The routers use HDLC as the default
encapsulation method for data transmission. All the
transaction between the departments of the company
is carried out over the network. However,
unfortunately, some important information of Finance
department regarding policies could not reach to the
Software Management department’s destination
computer because it was lost in transit.

Problem
Information was lost due to network congestion
in network

Suggested Solution
All the branches should be integrated using the
Frame Relay technology. Frame Relay provides a
congestion control mechanism that can prevent the
loss of critical data

Frame Relay Backup using ISDN

Troubleshooting Frame Relay
 The commons issues in the Frame Relay can be
resolved using the debug command
 This command enables you to troubleshoot the
Frame Relay connections
 You can use the router console to enter these
commands:
 debug frame-relay events Command
 debug Frame Relay packet Command

Summary - I
 Frame Relay networks are multi-access networks where
more than two devices can be attached to the network
 A Virtual circuit (VC) represents the path on which the
frame travels. Virtual circuits enable you to compare
Frame Relay to leased physical circuit. There two types
of virtual circuits are:
 Permanent virtual circuit (PVC)
 Switched virtual circuit (SVC)
 LMI is the definition used between the Frame Relay DTE
and Frame Relay DCE, which means that the data send
by the DTE is processed between them

Summary - II
 Sometimes you might face problems with the
connection to the carrier switch. The commands
available are to troubleshoot LMI are:
 show interfaces
 show frame-relay lmi
 debug frame-relay lmi
 The DLCI identifies a virtual circuit for the Frame
Relay to forward the frames to appropriate remote
site when multiple access list use the same access
list

Summary - III
 The Frame Relay implementation of Cisco provides
with three different options to assign subnets and IP
address on the Frame Relay interfaces. The options
are:
 A subnet that contains all the Frame Relay data
terminal equipments (DTE)
 A subnet for each virtual circuit
 Hybrid of the above two
 Frame Relay networks use Asynchronous Transfer
Mode (ATM) in the core of the Frame Relay network

CCNA CHAPTER 11 BY jetarvind kumar madhukar

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