Local Management Interface (LMI)
Take a attending at Table 11.8.
Local Management Interface (LMI) is a signaling accepted acclimated amid your router and
the aboriginal Frame Relay about-face to which it’s connected. It allows for casual advice about
the operation and cachet of the basic ambit amid the provider’s arrangement and the DTE
(your router). It communicates advice about the following:
Keepalives These verify that abstracts is flowing.
Multicasting This is an alternative addendum of the LMI blueprint that allows, for example,
the able administration of acquisition advice and ARP requests over a Frame Relay network.
Multicasting uses the aloof DLCIs from 1019 through 1022.
TABLE 1 1 . 8 Configuring the LMI
Command Meaning
frame-relay lmi-type blazon Sets the LMI blazon on the Frame Relay interface
Global acclamation This provides all-around acceptation to DLCIs, acceptance the Frame Relay
cloud to assignment absolutely like a LAN.
Status of basic circuits This provides DLCI status. The cachet inquiries and letters are
used as keepalives back there is no approved LMI cartage to send.
But remember, LMI is not advice amid your routers; it’s communication
between your router and the abutting Frame Relay switch. So, it’s absolutely accessible that the
router on one end of a PVC is actively accepting LMI while the router on the added end of
the PVC is not. And of course, PVCs won’t assignment with one end down. (I say this to analyze the
local attributes of LMI communications.)
There are three altered types of LMI bulletin formats: Cisco, ANSI, and Q.933A. The different
kinds in use depend on both the blazon and the agreement of the telco’s switching gear,
so it’s acute that you configure your router for the actual format, which should be
provided by the telco.
On Cisco equipment, the absence blazon is, surprise, Cisco, but you still ability accept to change
to ANSI or Q.933A depending on what your account provider tells you. The three different
LMI types are apparent in the afterward router output:
RouterA(config-if)#frame-relay lmi-type ?
cisco
ansi
q933a
As apparent in the output, all three accepted LMI signaling formats are supported. Here’s a
description of each:
Cisco LMI was authentic by the Gang of Four (default). The Local Management Interface
(LMI) was developed in 1990 by Cisco Systems, StrataCom, Northern Telecom, and Digital
Equipment Corporation and became accepted as the Gang-of-Four LMI, or Cisco LMI.
ANSI Annex D is included with ANSI accepted T1.617.
ITU-T (Q.933A) Annex A is included in the ITU-T accepted and authentic by application the
Q.933a command keyword.
Routers accept LMI advice from the account provider’s Frame Relay about-face on a
frame-encapsulated interface and amend the basic ambit cachet to one of three different
states:
Active accompaniment Everything is up, and routers can barter information.
Inactive accompaniment The router’s interface is up and alive with a affiliation to the switching
office, but the alien router isn’t up.
Deleted accompaniment No LMI advice is actuality accustomed on the interface from the switch, which
could be because of a mapping botheration or a band failure.