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Configuring Frame Relay DLCIs

 

Understanding Frame Relay DLCIs

A Frame Relay interface can be a point-to-point interface or a point-to-multipoint (also called a multipoint non-broadcast multiaccess [NBMA]) connection.

When you are using Frame Relay encapsulation on an interface, each logical interface corresponds to one or more permanent virtual circuits (PVCs) or switched virtual circuits (SVCs). For each PVC or SVC, you must configure one data-link connection identifier (DLCI).

Configuring a Point-to-Point Frame Relay Connection

A point-to-point interface can have one DLCI. When you are configuring point-to-point connections, the MTU sizes on both sides of the connection must be the same.

To configure a point-to-point Frame Relay connection:

  1. In the 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. Include the dlci statement.

The DLCI identifier is a value from 16 through 1022. Numbers 1 through 15 are reserved for future use.

Note

For information about Frame Relay DLCI limitations for channelized interfaces, see Data-Link Connection Identifiers on Channelized Interfaces.

You configure the router to use DLCI sparse mode by including the sparse-dlcis statement at the [edit chassis fpc slot-number pic pic-number] hierarchy level. For more information about DLCI sparse mode, see the Junos OS Administration Library.

Configuring a Point-to-Multipoint Frame Relay Connection

When you are configuring point-to-multipoint connections, all interfaces in the subnet must use the same MTU size.

To configure a point-to-multipoint Frame Relay connection:

  1. In the configuration mode go to the [edit interfaces interface-name fpc/pic/port unit logical-unit-number family family address address] or [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number family family address address] hierarchy level.
  2. Include the multipoint-destination statement.

For each destination, include one multipoint-destination statement. address is the address of the remote side of the connection, and dlci-identifier is the DLCI identifier for the connection.

If keepalives are enabled, causing the interface to send LMI messages during idle times, the number of possible DLCI configurations is limited by the MTU selected for the interface. For more information, see Configuring Frame Relay Keepalives.

Configuring a Multicast-Capable Frame Relay Connection

By default, Frame Relay connections assume unicast traffic. If your Frame Relay switch performs multicast replication, you can configure the connection to support multicast traffic by including the multicast-dlci statement:

You can configure multicast support only on point-to-multipoint Frame Relay connections.

To configure a multicast-capable Frame Relay connection:

  1. In the 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. Include the multicast-dlci statement.

The DLCI identifier is a value from 16 through 1022 that defines the Frame Relay DLCI over which the switch expects to receive multicast packets for replication.

If keepalives are enabled, causing the interface to send LMI messages during idle times, the number of possible DLCI configurations is limited by the MTU selected for the interface. For more information, see Configuring Frame Relay Keepalives.