Configuring Frame Relay

Configure a Frame Relay interface by entering Interface Configuration mode. The procedure that follows is an example of a Frame Relay configuration on a serial interface. All tasks are mandatory unless otherwise noted.

1. From Configuration mode, enter the physical interface on which you want to configure Frame Relay.

host1(config)#interface serial 3/1:2/1

2. Select Frame Relay as the encapsulation method for the interface.

host1(config-if)#encapsulation frame-relay ietf

3. (Optional) Assign a text description or an alias to the interface.

host1(config-if)#frame-relay description boston01

4. Configure the interface as a DTE, DCE, or NNI.

host1(config-if)#frame-relay intf-type dte

5. Configure the LMI type.

host1(config-if)#frame-relay lmi-type ansi

6. (Optional) Configure Frame Relay counters and timers.

host1(config-if)#frame-relay lmi-n391dte 20

7. Configure the cyclic redundancy check (CRC).

host1(config-if)#crc 32

8. Create a subinterface.

host1(config-if)#interface serial 3/1:2/1.1

9. (Optional) Assign a text description or an alias to the subinterface.

host1(config-subif)#frame-relay description westford011

10. Add a circuit to a subinterface.

host1(config-subif)#frame-relay interface-dlci 17 ietf

11. Assign a local IP address to the circuit.

host1(config-subif)#ip address 192.32.10.2 255.255.255.0

12. Use show commands to verify that your configuration changes are correct by checking the state of the interfaces.

host1#show frame-relay lmi

host1#show frame-relay map

host1#show frame-relay pvc

13. (Optional) Disable the local management interface.

host1#no frame-relay keepalive

14. (Optional) Disable the interface.

host1(config-if)#shutdown

    crc

• Use to set the number of bits used for CRC.
• The CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data.
• 16 and 32 indicate the number of bits per frame that are used to calculate the frame check sequence (FCS).
• A 32-bit CRC transmits longer streams at faster rates and therefore provides better ongoing error detection, such as for an OC12/STM4 POS module.
• The default is 16. You must configure CRC (CRC16 or CRC32) to match the configuration on the other side of the Frame Relay connection.
• Example

host1(config-if)#crc 32

• Use the no version to set the CRC to the default value.

    encapsulation ietf

• Use to specify Frame Relay as the encapsulation method for the interface.
• The system uses IETF format (RFC 2427 encapsulation).
• Example

host1(config-if)#encapsulation frame-relay ietf

• Use the no version to remove Frame Relay configuration from an interface.

    frame-relay description

• Use to assign a text description or an alias to a Frame Relay interface or subinterface.
• You can use this command to help you identify the interface and keep track of interface connections.
• The description or alias can be a maximum of 80 characters.
• Use the show frame-relay interface or show frame-relay subinterface command to display the text description.
• Examples

host1(config-if)#frame-relay description boston01

host1(config-subif)#frame-relay description toronto011

• Use the no version to remove the text description or alias.

    frame-relay interface-dlci ietf

• Use to configure a Frame Relay permanent virtual circuit (PVC) over a subinterface.
• The ietf keyword is mandatory and indicates RFC 2427 encapsulation.
• Define a data-link connection identifier (DLCI) in the range 16-1007.
• To configure a Frame Relay PVC, you must specify a DLCI.
• Frame Relay service is offered in the form of PVCs. A PVC is a data-link connection that is predefined on both ends of the connection. A network operator assigns the endpoints of the circuit. Although the actual path taken through the network may vary from time to time, the beginning and end of the circuit do not change. This type of circuit behaves like a dedicated point-to-point circuit.
• PVCs are identified by DLCIs. A DLCI is a 10-bit channel number that is attached to data frames to tell a Frame Relay network how to route the data. Frame Relay is statistically multiplexed, which means that only one frame can be transmitted at a time, but many logical connections can coexist on a single physical line. The DLCI allows the data to be logically tied to one of the connections, so that when the data gets to the network, the network knows where to send it.
• DLCIs on the same physical line must match. However, DLCIs have local significance; that is, if the DLCIs are not on the same physical line, the end devices at two different ends of a connection may use a different DLCI to refer to the same connection.
• The system does not support switched virtual circuits (SVCs). An SVC is an any-to-any connection that can be established or removed as needed. With SVCs, you initiate calls using Frame Relay by requesting a destination address and assigning a DLCI, which is established for the duration of the call.
• Example

host1(config-subif)#frame-relay interface-dlci 17 ietf

• Use the no version to remove DLCI/PVC assignment.

    frame-relay intf-type

• Use to configure a Frame Relay interface circuit to operate as data communications equipment (DCE), data terminal equipment (DTE), or Network-to-Network Interface (NNI).
• Frame Relay provides packet-switching data communications between user devices and network equipment across the interface. User devices are referred to as DTE.
• Network equipment that interfaces with a DTE is referred to as a DCE.
• NNI provides a connection between two Frame Relay subnetworks.
• If your system is connected to a Frame Relay switch, configure the interface as a DTE. If your system is connected by a point-to-point line, configure one end as the DTE and the other as the DCE.
• Example

host1(config-if)#frame-relay intf-type dte

• Use the no version to set the default of DTE.

    frame-relay keepalive

• Use to enable the LMI on the interface.
• You can specify the keepalive interval in seconds.
• The value on the DTE should be less than the value set on the DCE.
• The default is 10 seconds.
• Example

host1#no frame-relay keepalive

• Use the no version to disable LMI on the interface.

    frame-relay lmi-type

• Use to configure one of the local management interface types.
• LMI provides configuration and status information relating to the virtual circuits operating over Frame Relay.
• LMI specifies polling mechanisms to receive incremental and full-status updates from the network.
• Systems conform to the following LMI specifications:

• ansi - ANSI-T1.617 Annex D
• q933a - ITU-T Q.933 Annex A
• cisco - original Group of Four specification developed by DEC, Northern Telecom, Stratacom, and Cisco
• none - suppresses LMI

• The default is cisco.
• Example

host1(config-if)#frame-relay lmi-type ansi

• Use the no version to return to the default LMI type.

    frame-relay lmi-n391dte
    frame-relay lmi-n392dce
    frame-relay lmi-n392dte
    frame-relay lmi-n393dce
    frame-relay lmi-n393dte
    frame-relay lmi-t391dte
    frame-relay lmi-t392dce

• Use to configure LMI counters and timers.
• LMI counters and timers have configurable ranges that allow you to control the state of the Frame Relay interface. In general, you should accept the default values for the timers and counters, unless you need to modify them according to a special arrangement with your customers.
• Some commands have DTE and DCE versions. Use the dte version of the command if the interface is operating as a DTE. Use the dce version of the command if the interface is operating as a DCE. Use both versions of the command if the interface is operating as an NNI.
• Use the frame-relay lmi-n391dte command to set the N391 full-status polling counter. When you set this counter to a number, n, the nth request is a full-status request. The range is 1-255 event messages. The default is 6 event messages.
• Use the frame-relay lmi-n392dte or frame-relay lmi-n392dce command to set the N392 error threshold counter, which specifies the number of errors within N393 events that will place the interface in an operationally down state. The range is 1-10. The default for the DTE version is 3. The default for the DCE version is 2.
• Use the frame-relay lmi-n393dte or frame-relay lmi-n393dce command to set the N393 monitored events counter to specify the diagnostic window used to verify link integrity. Detection of N392 errors within the window of N393 samples places the interface in an operationally down state. The range is 1-10 events. The default for the DTE version of the command is 4 events. The default for the DCE version is 2 events.
• Use the frame-relay lmi-t391dte command to set the T391 link integrity polling timer interval between status inquiries issued by the DTE. The network checks that the DTE polls within the verification interval, T392. The range is 5-30 seconds. The default is 10 seconds.
• Use the frame-relay lmi-t392dce command to set the T392 polling verification timer that specifies the maximum interval (in seconds) between the receipt of status inquiries from the DTE equipment before it considers it as an error event. The range is 5-30 seconds. The default is 15 seconds.
• Example

host1(config-if)#frame-relay lmi-n391dte 20

• Use the no version to remove the current setting and set the default.

    interface pos

• Use to configure a POS interface in slot/port format:

• A slot refers to a system chassis slot.
• A port refers to a line module port.

• Example

host1(config)#interface pos 0/1

• Use the no version to remove the POS interface.

    interface serial

• Use to configure a serial interface in the appropriate format by selecting a previously configured physical interface on which you want to configure Frame Relay. For example, for a CT3 interface use slot/port:channel/subchannel.
• Use to configure a Frame Relay subinterface in the appropriate format by selecting a previously configured physical interface. For example, for a T3-Frame interface use slot/port.subinterface, for a CT1/CE1 interface use slot/port.channel-group.subinterface.

Note: Before you configure Frame Relay, see the appropriate chapter in this guide for details on configuring physical interfaces.

• slot - system chassis slot
• port - CT3, T3, E3, CT1, or CE1 module I/O port
• channel - T1 (DS1) channel
• subchannel - set of DS0 timeslots. Refer to the Fractional T1 section in ERX Physical Layer Configuration Guide, Chapter 1, Configuring Channelized T3 Interfaces.
• subinterface - user-assigned nonnegative number that identifies a Frame Relay subinterface
• channel-group - CT1 or CE1 channel group number in the range 1-24 (CT1 and J1) and 1-31 (CE1)

• Example

host1(config-if)#interface serial 3/1:2/1.1

• Use the no version to remove the subinterface or the serial interface.

    ip address

• Use to assign an IP address and subnet mask to a subinterface.
• Example

host1(config-subif)#ip address 192.32.10.2 255.255.255.0

• Use the no version to remove an IP address or to disable IP processing.

    pos description

• Use to assign a text description or an alias to a POS HDLC interface.
• You can use this command to help you identify the interface and keep track of interface connections.
• The description or alias can be a maximum of 80 characters.
• Use the show interfaces pos command to display the text description. For details, see the Monitoring POS section in Chapter 5, Configuring Packet over SONET.
• Example

host1(config-if)#pos description austin01 pos interface

• Use the no version to remove the text description or alias.

    serial description

• Use to assign a text description or an alias to a serial HDLC interface.
• You can use this command to help you identify the interface and keep track of interface connections.
• The description or alias can be a maximum of 80 characters.
• Use the show interfaces serial command to display the text description. For example, for a CT3 interface, see the Monitoring Interfaces section in ERX Physical Layer Configuration Guide, Chapter 1, Configuring Channelized T3 Interfaces.
• Example

host1(config-if)#serial description ottawa012 hdlc channel

• Use the no version to remove the text description or alias.

    sleep

• Use to disable a Frame-Relay interface.
• Use the no version to restart a disabled interface.