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Configuring Frame Relay Interface Encapsulation

 

Understanding Frame Relay Interface Encapsulation

Point-to-Point Protocol (PPP) encapsulation is the default encapsulation type for physical interfaces. You must configure an encapsulation for physical interfaces that do not support PPP encapsulation. You can optionally configure an encapsulation on a logical interface.

When you configure a multipoint encapsulation (such as Frame Relay), the physical interface can have multiple logical units, and the units can be either point-to-point or multipoint.

The encapsulation type can be one of the following:

  • Flexible Frame Relay (flexible-frame-relay)—IQ interfaces can use flexible Frame Relay encapsulation. You use flexible Frame Relay encapsulation when you want to configure multiple per-unit Frame Relay encapsulations. This encapsulation type allows you to configure any combination of TCC, CCC, and standard Frame Relay encapsulations on a single physical port. Also, each logical interface can have any data-link connection identifier (DLCI) value from 1 through 1022.

  • Frame Relay (frame-relay)—Defined in RFC 1490. E1, E3, link services, SONET/SDH, T1, T3, and voice services interfaces can use Frame Relay encapsulation. Five related versions are supported:

    • Circuit cross-connect (CCC) version (frame-relay-ccc)—Standard Frame Relay is used for DLCIs 0 through 511. DLCIs 512 through 1022 are dedicated to CCC. The logical interface must also have frame-relay-ccc encapsulation. When you use this encapsulation type, you can configure the ccc family only.

    • Translational cross-connect (TCC) version (frame-relay-tcc)—Similar to Frame Relay CCC and has the same configuration restrictions, but used for circuits with different media on either side of the connection.

    • Extended CCC version (extended-frame-relay-ccc)—This encapsulation type allows you to dedicate DLCIs 1 through 1022 to CCC. The logical interface must have frame-relay-ccc encapsulation. When you use this encapsulation type, you can configure the ccc family only.

    • Extended TCC version (extended-frame-relay-tcc)—Similar to extended Frame Relay CCC, this encapsulation type allows you to dedicate DLCIs 1 through 1022 to TCC, which is used for circuits with different media on either side of the connection.

    • Port CCC version (frame-relay-port-ccc)—Defined in the Internet Engineering Task Force (IETF) document, Frame Relay Encapsulation over Pseudo-Wires (expired December 2002). This encapsulation type allows you to transparently carry all the DLCIs between two customer edge (CE) routers without explicitly configuring each DLCI on the two provider edge (PE) routers with Frame Relay transport. The connection between the two CE routers can be either user-to-network interface (UNI) or network-to-network interface (NNI); this is completely transparent to the PE routers. The logical interface does not require an encapsulation statement. When you use this encapsulation type, you can configure the ccc family only.

  • Frame Relay Ether Type (frame-relay-ether-type)—Physical interfaces can use Frame Relay ether type encapsulation for compatibility with Cisco Frame Relay. IETF frame relay encapsulation identifies the payload format using NLPID and SNAP formats. Cisco-compatible Frame Relay encapsulation uses the Ethernet type to identify the type of payload. Two related versions are supported:

    • TCC version (frame-relay-ether-type-tcc)—Cisco-compatible Frame Relay for DLCIs 0 through 511. DLCIs 512 through 1022 are dedicated to TCC. This encapsulation is used for circuits with different media on either side of the connection.

    • Extended TCC version (extended-frame-relay-ether-type-tcc)—This encapsulation allows you to dedicate Cisco-compatible Frame Relay TCC for DLCIs 1 through 1022. This encapsulation is used for circuits with different media on either side of the connection. Extended Frame Relay ether type TCC encapsulation is supported on the same PICs as extended Frame Relay TCC encapsulation.

Note

When the encapsulation type is set to Cisco-compatible Frame Relay encapsulation, ensure that the LMI type is set to ANSI or Q933-A.

Support for extended Frame Relay and flexible Frame Relay differs by PIC type, as shown in Table 1.

Table 1: PIC Support for Enhanced Frame Relay Encapsulation Types

PIC Type

Extended Frame Relay CCC

Extended Frame Relay TCC

Flexible Frame Relay

Intelligent Queuing

1-port Channelized CHOC12 IQ

Yes

Yes

Yes

4-port Channelized DS3 IQ

Yes

Yes

Yes

10-port Channelized E1 IQ

Yes

Yes

Yes

4-port E3 IQ

Yes

Yes

Yes

1-port Channelized STM1 IQ

Yes

Yes

Yes

4-port OC48/STM16 Type 3 PIC

Yes

Yes

Yes

SONET/SDH

1-port OC12

Yes

Yes

No

2-port OC3

Yes

Yes

No

1-port OC48

Yes

Yes

No

1-port OC192

Yes

Yes

No

1-port STM16 SDH, SMSR

Yes

Yes

No

 
Others

4-port E1

No

No

No

4-port T1

No

No

No

4-port T3

No

No

No

10-port Channelized E1

No

No

No

2-port Channelized DS3

No

No

No

1-port Channelized OC12, SMIR

No

No

No

4-port Channelized DS3

No

No

No

1-port Channelized STM1, SMIR

No

No

No

16-port Channelized T1/E1 Circuit Emulation MIC

Yes

Yes

Yes

2-port Serial

No

No

No

Configuring the Frame Relay Encapsulation on a Physical Interface

Frame Relay encapsulation on the physical interface is defined in RFC 1490, Multiprotocol Interconnect over Frame Relay. E1, E3, link services, SONET/SDH, T1, T3, and voice services interfaces can use Frame Relay encapsulation.

To configure encapsulation on a physical interface:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Configure the encapsulation type as described in encapsulation.

Configuring the Frame Relay Encapsulation on a Logical Interface

Generally, you configure encapsulation of an interface at the [edit interfaces interface-name] hierarchy level. However, for Frame Relay encapsulation, you can also configure the encapsulation type that is used inside the Frame Relay packet itself.

To configure encapsulation on a logical interface:

  1. In configuration mode, go to the [edit interfaces interface-name unit logical-unit-number] or [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number] hierarchy level.
  2. Configure the encapsulation type as described in encapsulation (Logical Interface) and specify frame-relay-ccc, frame-relay-ppp, frame-relay-tcc, frame-relay-ether-type, or frame-relay-ether-type-tcc option.

Example: Configuring the Encapsulation on a Physical Interface

Configure Frame Relay encapsulation on a SONET/SDH interface. The second and third family statements allow Intermediate System-to-Intermediate System (IS-IS) and Multiprotocol Label Switching (MPLS) to run on the interface.