How to configure Frame Relay Step by Step Guide

Frame Relay is one of the most widely used and highly tested WAN solutions in networking certification programs. This tutorial explains how to configure, test, and verify it on Cisco routers.

Lab setup

Build a practice lab as shown in the following image. You can use real devices or any network simulator software for this. This tutorial uses Packet Tracer network simulator software. It also provides download links for the lab created in this tutorial with various configuration steps.

Download Frame Relay Practice Lab (Without configuration)

This network consists of two routers connected through a Frame Relay cloud. At this stage, no configuration has been applied to any device.

Creating virtual circuits

Frame Relay uses virtual circuits to connect networks. A virtual circuit needs a few essential settings and configuration values. In the real world, the Frame Relay service provider does the necessary settings and provides these parameters. In a lab environment, you need to manually adjust these settings.

Click Cloud-PT and click Config. From the left pane, select the interface connected to the router.

LMI

Frame Relay supports three LMI options: ANSI, Cisco, and Q933a. You can select any option here. However, you must select the same option on the connected serial interface. For example, if you select Cisco here, you must set the LMI type to Cisco on the connected serial interface.

DLCI

The DTE device (connected serial interface) identifies the virtual circuit using the DLCI number. You can pick any unique number here. However, you must use the same DLCI number on the connected serial interface.

Connection Name

It assigns a name to the virtual circuit. You can use this name to identify the virtual circuit on the Frame Relay device.

Follow the same process and configure the LMI and DLCI number for the interface connected to the second router.

The next step is to link the virtual circuit (VC). Select the Frame Relay option from the left pane. In the right window, select the appropriate interface and connection from the dropdown menu to represent one end of the VC. For the opposite end, select the corresponding connection and interface from the right-side dropdown menu.

R1 is connected to Serial 0, and a connection named R1toR2 has been created. On the left side, select Serial 0 and R1toR2.

R2 is connected to Serial 1, and a connection named R2toR1 has been created. On the right side, select Serial 1 and R2toR1.

After selecting values for both ends, click the Add button.

Frame Relay connects two sites via a virtual circuit (VC). The service provider uses its internal infrastructure to build VCs. Neither the end user nor the provider requires knowledge of the underlying technology. The Frame Relay provider does not share these details with users. End users only need to know which VC connects to which site. For this purpose, Frame Relay assigns two DLCI values to each VC, one for each end. The end user uses this value to identify the other end of the VC.

In a real-world environment, these values are provided by the Frame Relay provider to the customer. The customer configures these values on the DTE router connected to the Frame Relay device. In this example, these values are as follows.

Frame Relay configuration on the DTE (router) device

All Frame Relay-related configuration goes in the interface configuration mode of the device connected to the Frame Relay device.

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#

Testing Frame Relay configuration

To test the Frame Relay configuration, you can check connectivity between both routers. Send the ping request from R1. If it gets replies, it verifies the Frame Relay configuration.

Download Frame Relay Practice Lab (With configuration)

Frame Relay configuration (Example 2)

The previous section covered a basic Frame Relay configuration example. This section provides a more advanced Frame Relay setup, focusing on additional features such as point-to-point and point-to-multipoint configurations. Build a practice lab as shown in the following image, or download the prebuilt lab and open it with Packet Tracer.

Download the advanced Frame Relay practice Lab ( with initial configuration)

Frame Relay supports two network topologies: fully meshed and partially meshed. In a fully meshed network, all sites are directly connected to each other. In a partially meshed network, not all sites are directly linked to another site. This example covers both network types. The connections between R1, R2, and R3 form a fully meshed network, while a direct connection between R1 and R4 builds a partially meshed network.

Fully Meshed Network Configuration (Multipoint)

Partially Meshed Network Configuration (Point-to-point)

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#

In this configuration, R1 is connected to three sites using a single serial interface. To enable connections to multiple sites from a single interface, subinterfaces are required. A sub-interface is a virtual interface defined by the IOS software. It uses the same physical hardware as the main interface but operates as a separate interface.

A sub-interface can work in two modes: point-to-point and multipoint.

In point-to-point mode, a sub-interface connects with a single virtual circuit. Each sub-interface requires its own IP subnet, and each IP address must be mapped to a unique DLCI address.

In multipoint mode, a sub-interface connects with multiple virtual circuits. A single IP address can be mapped to multiple DLCI addresses. This mode is typically used in fully meshed networks where each router is connected to all others.

Before creating a sub-interface, you must set encapsulation on the physical interface. The physical interface must be enabled using the no shutdown command and should remain enabled at all times. Disabling the physical interface will disable all associated sub-interfaces. Since sub-interfaces use their own IP configuration, an IP address cannot be assigned to the physical interface.

The following command creates a sub-interface on the serial interface. Since this sub-interface connects to two sites, it uses multipoint mode.

Router(config-if)#interface serial 0/0/0.1 multipoint

The following command sets a common IP address for all VCs connected from this interface. In multipoint mode, a single IP subnet can be used for multiple VCs. This IP address is used to connect with both sites (VCs).

Router(config-subif)#ip address 192.168.1.1 255.255.255.0

Frame Relay provides LMI options and DLCI numbers. The LMI option is used to exchange management messages between the router and the Frame Relay switch, while the DLCI number identifies the other end of the virtual circuit.

In this example, the virtual circuit with DLCI number 100 connects to R2. The virtual circuit with DLCI number 101 connects to R3. The router automatically maps the DLCI number to the correct virtual circuit. You only need to provide the DLCI numbers associated with the interface.

The following commands accomplish this for the sub-interfaces.

Router(config-subif)#frame-relay interface-dlci 100
Router(config-subif)#frame-relay interface-dlci 101

You also need to adjust the LMI type if it is different from the default. Since this example uses the default LMI type, you do not need to set or adjust it. If the Cisco router is running IOS version 11.2 or higher, the interface will automatically detect the appropriate LMI type.

R1 has an additional point-to-point connection. For this connection, a separate sub-interface is required. The following command creates another point-to-point sub-interface.

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

The following command assigns an IP address to the interface.

Router(config-subif)#ip address 192.168.2.1 255.255.255.0

The next command assigns the associated DLCI number to it.

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

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#

R3

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 192.168.1.3 255.255.255.0
Router(config-subif)#frame-relay interface-dlci 100
Router(config-subif)#frame-relay interface-dlci 101
Router(config-subif)#exit
Router(config)#exit
Router#

R4

Router>enable
Router#configure terminal
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#

Verifying Frame Relay configuration

Check connectivity between routers to test and verify the Frame Relay configuration.

Download the advanced Frame Relay practice Lab ( with the Frame Relay configuration)

Frame Relay configuration commands sheet

Conclusion

This tutorial has demonstrated how to configure, test, and verify Frame Relay on Cisco routers using Packet Tracer, covering both basic and advanced scenarios. By understanding concepts such as virtual circuits, DLCI, LMI types, and sub-interfaces, you can confidently set up Frame Relay networks in lab environments or for certification preparation.