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NG_LMI(4) Device Drivers Manual NG_LMI(4)


ng_lmiframe relay LMI protocol netgraph node type


#include <sys/types.h>
#include <netgraph/ng_lmi.h>


The lmi node type performs the frame relay LMI protocol. It supports the ITU Annex A, ANSI Annex D, and Group-of-four LMI types. It also supports auto-detection of the LMI type.

To enable a specific LMI type, connect the corresponding hook (annexA, annexD, or group4) to DLCI 0 or 1023 of a ng_frame_relay(4) node. Typically, Annex A and Annex D live on DLCI 0 while Group-of-four lives on DLCI 1023.

To enable LMI type auto-detection, connect the auto0 hook to DLCI 0 and the auto1023 hook to DLCI 1023. The node will attempt to automatically determine which LMI type is running at the switch, and go into that mode.

Only one fixed LMI type, or auto-detection, can be active at any given time.

The NGM_LMI_GET_STATUS control message can be used at any time to query the current status of the LMI protocol and each DLCI channel. This node also supports the NGM_TEXT_STATUS control message.


This node type supports the following hooks:

ITU Annex A LMI hook.
ANSI Annex D LMI hook.
Group-of-four LMI hook.
Auto-detection hook for DLCI 0.
Auto-detection hook for DLCI 1023.


This node type supports the generic control messages, plus the following:

This command returns status information in a struct nglmistat:
#define NGM_LMI_STAT_ARYSIZE   (1024/8)

struct nglmistat {
  u_char  proto[12];	/* Active proto (same as hook name) */
  u_char  hook[12];	/* Active hook */
  u_char  fixed;	/* If set to fixed LMI mode */
  u_char  autod;	/* If currently auto-detecting */
  u_char  seen[NGM_LMI_STAT_ARYSIZE];	/* DLCIs ever seen */
  u_char  up[NGM_LMI_STAT_ARYSIZE];	/* DLCIs currently up */
This generic message returns is a human-readable version of the node status.


This node shuts down upon receipt of a NGM_SHUTDOWN control message, or when all hooks have been disconnected.


netgraph(4), ng_frame_relay(4), ngctl(8)

ANSI T1.617-1991 Annex D.

ITU-T Q.933 Digital Subscriber Signaling System No. 1 - Signaling Specification for Frame Mode Basic Call Control, Annex A.


The ng_lmi node type was implemented in FreeBSD 4.0.


Julian Elischer <>

November 13, 2012 Debian