So... continuing with our Frame-Relay stuff, let´s take a look at our friend Local Management Interface (or LMI, as it preffers to be called). ;)
LMI is the protocol that exchanges information between your Router and the Frame-Relay Switch, it´ll carry information about DLCI status, Keepalives, etc. You can monitor the LMI traffic from your Router using the "debug frame-relay lmi" command.
Follows an output from a debug:
R1#debug frame-relay lmi
*Mar 1 00:16:43:Serial1/0(out):StEnq,myseq 61,yourseen 60,DTE up
So, what can we understand about this output!? Hmmm... good question! Just checking it, we can identify that the first part is just a normal Keepalive, and the second one means a Full Status Update... Here is how we checked it:
Type 1 - is a Normal Keepalive (sent every 10 seconds by default)
Type 0 - is a Full Status Update, it is sent every 6th Keepalive, that means, if you don´t change the defaults, it´ll be sent every 60 seconds, and it´ll include the DLCI status, which can be:
-> 0x0 means "inactive"
-> 0x2 means "active" (the status we normally want!)
-> 0x3 means that the active DLCI cannot accept more traffic without drops ocurring - kind of a flow-control code
-> 0x4 means "deleted"
So, checking the previous output we can see dlci 102, status 0x2, that means DLCI 102 is Active!
We can also check that using the "show frame-relay pvc" command:
R1#sh frame-relay pvc
PVC Statistics for interface Serial1/0 (Frame Relay DTE)
Active Inactive Deleted Static
DLCI=102, DLCI USAGE=LOCAL, PVC STATUS=ACTIVE,INTERFACE=Serial1/0
input pkts 11 output pkts 7 in bytes 1074
DLCI=103, DLCI USAGE=LOCAL, PVC STATUS=ACTIVE,INTERFACE=Serial1/0
input pkts 1 output pkts 4 in bytes 34
There are some good fields to be checked in this output, for example, the PVC STATUS and the DLCI USAGE.
The PVC Status can can have four possible states:
ACTIVE - PVC is up and functioning normally.
INACTIVE - PVC is not up end-to-end. This can be caused by several problems, like incorrect mapping (or no mapping at all) for the local DLCI in the frame-relay cloud, or the remote end of the PVC is Deleted!
DELETED - Either there´s no LMI being exchanged between the router and the local frame-relay switch (normally from PTT), or the frame-relay switch (again, normally this frame-relay switch belongs to the PTT) doesn´t have this specific DLCI configured.
STATIC - No keepalive configured on the frame-relay interface of the router.
And finally, the DLCI USAGE field can have one of the following entries:
SWITCHED - that means, this router is been used as a Frame-Relay Switch.
LOCAL - the Router is used as a Data Terminal Equipment (DTE).
UNUSED - the DLCI is not configured on the router (that means, you haven´t configured this DLCI under any interface).
Some good references at Cisco´s Website are: