Cisco LMI Support Options For Frame Relay T1 Circuits

Cisco supports three different Local Management Interface (LMI) types for Frame Relay:

1. Cisco


2. ANSI Annex D


3. Q933-A Annex A

Beginning with Cisco IOS Software Release 11.2, the LMI autosense feature allows a Frame Relay interface to autodetect the LMI type supported by the directly connected Frame Relay switch. Based on the LMI status messages it receives from the Frame Relay switch, the router automatically configures its Frame Relay interface with the supported LMI type acknowledged by the Frame Relay switch.

No extra configuration command is required on a Cisco router to activate the LMI autosense feature. With Cisco IOS Release 11.2 or later, LMI autosense is activated by default when an LMI type is not explicitly configured on the interface.

After the no shutdown interface configuration command is used to activate the Frame Relay interface, the interface starts polling the Frame Relay switch for the supported LMI type by sending out LMI status requests for all three supported LMI types—ANSI, Q933-A, and Cisco—in quick succession.