CCNA Study Guide

This tutorial explains How to configure Frame Relay step by step in Cisco Routers, How to configure LMI option and DLCI number in Frame Relay, How to create point-point and multipoint connection in frame Relay, How to create frame Relay sub interface, how to simulate frame relay in packet tracer and how to verify Frame Relay implementation in detail with example including Frame Relay configuration commands sheet.

You can follow this tutorial on any network simulator software or even on real Cisco devices (if you can afford them for practice). I personally prefer Packet Tracer network simulator software.

We will start with the simplest example of Frame Relay. Once we understood first example, we will add more terms in next example. This easy approach will help us to learn Frame Relay configuration easily.

This tutorial is the last part of our article "WAN Terminology Explained with Encapsulation Protocols and Methods". You can read other parts of this article here.

WAN Tutorial – Basic WAN Switching Concept Explained

This tutorial is the first part of article. This part explains basic wan concepts including terminology, encapsulation methods, switching concepts and encapsulation protocols in detail with example.

HDLC Protocol and Encapsulation method Explained

This tutorial is the second part of the article. This part explains HDLC (High-Level Data Link Control) protocol and encapsulation method in detail with examples including step by step configuration guide.

PPP Protocol and Encapsulation method Explained

This tutorial is the third part of the article. This part explains PPP (Point to Point) protocol and encapsulation method in detail with examples including step by step configuration guide.

Basic Concepts of Frame Relay Explained in Easy Language

This tutorial is the fourth part of the article. This part explains basic concepts of Frame Relay such as LMI Types, DLCI, Access Rate, CIR rate, PVC, SVC and network type in easy language.

Create a topology as illustrate in following figure or download this pre-created topology.

Download Frame Relay Practise LAB - Blank

frame relay practice topology

This is the simplest example of Frame Relay network. It includes only two routers and one frame relay cloud. Both routers connected with each other via Frame Relay cloud. At this time there is no configuration in any device.

In real life Frame Relay provider company builds VCs but in LAB environment we have to bear this responsibility.

Frame Relay Configuration in Packet Tracer step by step

To simulate VCs in packet tracer following steps are required :-

Click Cloud-PT and click Config. From left pane select appropriate interface.

configure frame relay in packet tracer step 1

LMI :- Frame Relay supports three LMI options; ANSI, Cisco and Q933a. Whatever option we choose here, we have to use the same option at DTE ( serial 0/0/0 interface of router).

DLCI :- DTE device will identify this VC from DLCI number. Whatever number (usually 17 to 1000) we use here, we must have to use the same number at DTE. DLCI number must be unique for a Frame Relay interface.

Connection Name :- Connection name is used to map VCs between interfaces.

configure frame relay in packet tracer step 2
On Job

LMI option and DLCI number are provided by Frame Relay company.

Follow the same process and configure LMI and DLCI number for serial 1 interface.

configure frame relay in packet tracer step 3

Now finally it’s time to link this VC. Select Frame Relay option from left pane. In Right window select interface and connection from dropdown box. This represent one end of VC. For other end of VC we need to select appropriate connection and interface from right side dropdown boxes.

R1 is connected on Serial 0 and we have created a connection naming R1toR2. So in left side we will select Serial 0 and R1toR2.

R2 is connected on Serial 1 and we have created a connection naming R2toR1. So in right side we will select Serial 1 and R2toR1.

Once we are done click add button.

configure frame relay in packet tracer step 1

Frame Relay connects two sites via VC (Virtual Circuit). Service [Frame Relay] provider company uses its internal infrastructure to build VCs. Neither end user need to know this technology nor provider company share this information with users. All the end user need to know is which VC is connected with which site. For this information Frame Relay assigns two DLCI values in each VC, one for each end. End user uses this value to identify the other end of VC. Previous part of this article explains these terms in more detail.

Just like real life environment, we ( Frame Relay ) need to share LMI option and DLCI number with DTE (customer). In our example these values will be following

For R1

LMI option – ANSI

DLCI Number – 100

For R2

LMI option – Cisco

DLCI Number – 101

That’s all setting we need in packet tracer to simulate Frame Relay. Now it’s time to configure DTE ends. We need following essential configuration on both routers to bring this network up.

R1
Router>enable
Router#configure terminal
Router(config)#interface serial 0/0/0
Router(config-if)#encapsulation frame-relay
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config-if)#frame-relay interface-dlci 100
Router(config-if)#frame-relay lmi-type ansi
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#
R2
Router>enable
Router#configure terminal
Router(config)#interface serial 0/0/0
Router(config-if)#encapsulation frame-relay
Router(config-if)#ip address 192.168.1.2 255.255.255.0
Router(config-if)#frame-relay interface-dlci 101
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#

Let’s understand above configuration step by step. As we know, routers allow us to run different WAN services on different interfaces. So our first logical objective is to identify the correct interface. As figure shows interface serial 0/0/0 is assigned for frame relay on both routers. To configure Frame Relay on this interface we need to enter in interface mode. First three commands in above configuration are used for this purpose.

enable :- This command is used to enter in privileged exec mode.

configure terminal :- This command is used to enter in global configuration mode.

interface serial 0/0/0 :- This command is used to enter in interface mode.

In Cisco routers default encapsulation is set to HDLC. We cannot use Frame Relay with default encapsulation. Next command changes this encapsulation.

Router(config-if)#encapsulation frame-relay :- This command will change default encapsulation method to Frame Relay.

Next command assigns IP address in interface.

Router(config-if)#ip address 192.168.1.1 255.255.255.0:- This command assign IP address in Serial 0/0/0 of R1.

Router(config-if)#ip address 192.168.1.2 255.255.255.0 :- This command assign IP address in Serial 0/0/0 of R2.

Next command assigns DLCI value in interface.

Router(config-if)#frame-relay interface-dlci 100 :- This command assigns DLCI value 100 in Serial interface of R1.

Router(config-if)#frame-relay interface-dlci 101 :- This command assigns DLCI value 101 in Serial interface of R2.

Next command sets LMI option in interface. Until we change LMI option with next command default LMI option is set to Cisco (in Cisco routers).

Router(config-if)#frame-relay lmi-type ansi :- This command will change default LMI option to ANSI.

Have you notice ? we did not run this command in R2. Since LMI option [Cisco] that we got from provider matches with the default (Cisco) setting, so there is no need to run this command in R2.

By default all interfaces on router are disabled. We need to enable them before they can communicate with other.

Router(config-if)#no shutdown :- This command will enable the Serial interface.

Last two commands [exit] are used to return back in privileged exec mode.

That’s all configuration we need to do in routers.

Let’s test our implementation with ping command.

test frame relay

If ping return with success, move in next section. Otherwise check your configuration again. For troubleshooting you can use my configured topology.

Download Frame Relay Practise LAB - Configured

Now we are familiar with Frame Relay basic configuration. In next section we will understand advance configuration options with a complex example.

Frame Relay configuration example

Create a topology as illustrate in following figure or download this pre-created topology

Download Frame Relay Example Practise LAB - Blank

frame relay packet tracer practice lab

Frame Relay supports two types of network; fully meshed and partially meshed.

Fully meshed :- A network where all sites are connected with each other’s via direct link.

Partially meshed :- A network where all sites do not have direct link.

Previous part of this article explains these types in detail with examples.

To understand fully meshed network we will connect R1, R2 and R3 via direct links. To get an overview of partially meshed network we will connect R4 only with R1.

Fully Meshed Network Configuration (Multipoint)

Device Interface IP Address DLCI Number Connected with
R1 Sub-Serial 0/0/0.1 192.168.1.1/24 100 R2
R1 Sub-Serial 0/0/0.1 192.168.1.1/24 101 R3
R2 Sub-Serial 0/0/0.1 192.168.1.2/24 100 R1
R2 Sub-Serial 0/0/0.1 192.168.1.2/24 101 R3
R3 Sub-Serial 0/0/0.1 192.168.1.3/24 100 R1
R3 Sub-Serial 0/0/0.1 192.168.1.3/24 101 R2

Partially Meshed Network Configuration (Point-to-point)

Device Interface IP Address DLCI Number Connected with
R1 Sub-Serial 0/0/0.2 192.168.2.1/24 102 R4
R4 Serial 0/0/0 192.168.2.2/24 100 R1
frame relay example

Following commands will be used to configure the R1.

Router – R1
Router>enable
Router#configure terminal
Router(config)#interface serial 0/0/0
Router(config-if)#encapsulation frame-relay
Router(config-if)#no shutdown
Router(config-if)#interface serial 0/0/0.1 multipoint
Router(config-subif)#ip address 192.168.1.1 255.255.255.0
Router(config-subif)#frame-relay interface-dlci 100
Router(config-subif)#frame-relay interface-dlci 101
Router(config-subif)#interface serial 0/0/0.2 point-to-point
Router(config-subif)#ip address 192.168.2.1 255.255.255.0
Router(config-subif)#frame-relay interface-dlci 102
Router(config-subif)#exit
Router(config)#exit
Router#

As we know from pervious example, Frame Relay can be configured from interface mode. We used first three commands to access the interface mode. Next command is used to change default encapsulation method to Frame Relay. Fifth command is used to enable the interface. These five commands are explained in previous example.

Okay Let’s understand remaining commands.

As we can see in figure R1 is connected with three sites from single serial interface. To connect multiple sites from single interface we have to divide it in sub interfaces.

Sub-interface is a virtual interface defined by IOS software. It uses the same hardware of physical interface but works just like a separate interface.

A sub-interface can works in two modes; point-to-point and multipoint.

In point-to-point mode, sub-interface can connect with single VC. In this mode each sub-interface requires its own IP subnet. Each IP address need to be map with unique DLCI address.

In multipoint mode, sub-interface can connect with multiple VCs. A single IP address can be mapped with multiple DLCI addresses. Usually this mode is used in fully meshed network type where routers are connected with all routers.

Key points

Before we create sub interface, we first need to set encapsulation on physical interface. Physical interface need to be enabled from no shutdown command and it should be remain enabled always. If we disable the physical interface, all associate sub-interface will be disabled. Since sub-interfaces use their own IP configuration we cannot assign IP address in physical interface.

Following command will create a sub-interface from serial interface.

Router(config-if)#interface serial 0/0/0.1 multipoint :- Since this sub-interface will connect with two sites, multipoint mode will be used here.

Router(config-subif)#ip address 192.168.1.1 255.255.255.0 :- This command will set a common IP address for all VCs that we will connect from this interface. As we know in multipoint mode we are allowed to use a single IP subnet for multiple VCs. We will use this IP address to connect with both sites (VCs).

Frame Relay provides us LMI options and DLCI numbers. LMI option is used to exchange management messages between router and Frame Relay switch while DLCI number is used to identify the other end of VC. In our example VC that has DLCI number 100 is connected with R2 and VC with DLCI number 101 is connected with R3. Router will automatically map DLCI number with correct VC. We only need to provide the DLCI numbers which are associated with the interface. Following commands will do this job for this sub-interface.

Router(config-subif)#frame-relay interface-dlci 100

AND

Router(config-subif)#frame-relay interface-dlci 101

Since default LMI (Cisco) option is used in this example, we need not configure it here.

On Job

If Cisco router is running IOS version 11.2 or higher, interface will automatically detect corresponding LMI type.

R1 has one more point-to-point connection. For that connection we need a separate sub-interface. Following command will create another point-to-point sub-interface.

Router(config-subif)#interface serial 0/0/0.2 point-to-point

Following command will assign IP address in interface.

Router(config-subif)#ip address 192.168.2.1 255.255.255.0

Next command will assign associated DLCI number to it.

Router(config-subif)#frame-relay interface-dlci 102
Exam Tip

Point-to-point sub-interface map single DLCI and use a separate IP subnet. It also solve split horizon issue.

That’s all configuration we need on this router. We can use exit command to return back in global configuration mode or in privileged exec mode (from global configuration mode).

Same way we will configure R2 and R3.

Router - R2
Router>enable
Router#configure terminal
Router(config)#interface serial 0/0/0
Router(config-if)#encapsulation frame-relay
Router(config-if)#no shutdown
Router(config)#interface serial 0/0/0.1 multipoint
Router(config-subif)#ip address 192.168.1.2 255.255.255.0
Router(config-subif)#frame-relay interface-dlci 100
Router(config-subif)#frame-relay interface-dlci 101
Router(config-subif)#exit
Router(config)#exit
Router#
Router - R3
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface serial 0/0/0
Router(config-if)#encapsulation frame-relay
Router(config-if)#no shutdown
Router(config)#interface serial 0/0/0.1 multipoint
Router(config-subif)#ip address 192.168.1.3 255.255.255.0
Router(config-subif)#frame-relay interface-dlci 100
Router(config-subif)#frame-relay interface-dlci 101
Router(config-subif)#exit
Router(config)#exit
Router#

Router R4 has only one point-to-point link with R1. Since there is only one connection we can use physical interface for it or may create a logical interface as explained above, choice is ours.

Router - R4
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface serial 0/0/0
Router(config-if)#ip address 192.168.2.2 255.255.255.0
Router(config-if)#encapsulation frame-relay
Router(config-if)#frame-relay interface-dlci 100
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#

That’s all configuration we need to bring this frame relay network up. We can test our implementation with ping command. If everything is fine, routers should be able to access connected sites.

frame relay test implementation

You can use my configured topology for cross check.

Download Frame Relay Example Practise LAB - Configured

Frame Relay configuration command sheet

Command Description
Router(config-if)#encapsulation frame-relay Enable Frame Relay encapsulation in interface
Router(config-if)#encapsulation frame-relay ietf Enable Frame Relay ietf encapsulation in interface. Used if connecting with Non-Cisco router.
Router(config-if)#frame-relay lmitype {ansi | cisco | q933a} Used to set LMI type. If router is running Cisco ISO 11.2 or higher, this command is optional. As router will automatically detect the correct LMI type.
Router(config-if)#frame-relay interface-dlci 100 Assign DLCI number 100 in interface.
Router(config-if)#frame-relay map ip 192.168.100.1 110 broadcast Used to map remote IP with local DLCI statically. Mapping is automatically done by inverse ARP protocol.
By default Frame Relay does not forward any broadcast packet in VC. Due to this reason any routing protocol that depends on broadcast will not work with Frame Relay.
Use broadcast keyword to enable broadcast forwarding on this VC.
Router(config-if)#no frame-relay inverse arp Used to Turn off inverse ARP. If we turn off the inverse ARP, we have to map remote IP and local DLCI statically.
Router(config-if)#interface serial 0/0/0.1 point-to-point Creates a point-to-point sub-interface numbered 1
Router#show frame-relay map Used to view IP/DLCI map entries
Router#show frame-relay pvc Used to view the status of all PVCs configured
Router#show frame-relay lmi Displays LMI statistics including types and exchanged messages
Router#clear frame-relay counters Clears all Frame Relay counters
Router#clear frame-relay inarp Reset map table and Clears all Inverse ARP entries
Router#debug frame-relay lmi Enable debug process on LMI.
Router#no debug frame-relay lmi Disable debug process on LMI.

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