Right now, our Cisco router is sending the LMI type Cisco. We expect that, since Cisco is the default LMI type and we haven't changed it. show frame lmi verifies this.
R1#show frame lmi
LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 50 Num Status msgs Rcvd 50 Num Update Status Rcvd 0 Num Status Timeouts 0
The top line of the output indicates both the interface and the LMI type set on that interface. Here, it's the default of Cisco, since we haven't changed the LMI type -- yet.
The three fields that we're most interested in here are the two bolded fields and the "Num Status Timeouts" column. As the LMIs continue to be exchanged, the "Enq Sent" and "Msgs Rcvd" should continue to increment and the Timeouts value should remain where it is. Let's take another look at this output just a few minutes later.
R1#show frame lmi
LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0
Num Status Enq. Sent 64 Num Status msgs Rcvd 64
Num Update Status Rcvd 0 Num Status Timeouts 0
show interface serial 0 verifies that the interface is physically up and the line protocol (the logical state of the interface) is up as well. The keepalive for Frame Relay is set to 10 seconds - that's how often LMI messages are going out.
R1#show int s0 Serial0 is up, line protocol is up
Hardware is HD64570
Internet address is 172.12.123.1/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255 Encapsulation FRAME-RELAY, loopback not set Keepalive set (10 sec)
Now that we know how things look when the LMI matches, let's set the LMI type on the router to ansi and see what happens.
About 30 seconds later, the line protocol comes down.
R1(config)#int serial0
R1(config-if)#frame lmi-type ansi
R1(config-if)#
3d04h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
R1#show int s0
Serial0 is up, line protocol is down
We'll start troubleshooting this situation right after this brief, important message!
You and I know why the line protocol is down, since we did it deliberately. But what if you had just walked into a client site and they're complaining that their Frame Relay WAN link is down? The first step is to run show interface serial, which we just did. We see that the line protocol is down and that the interface is running Frame Relay.
The "Serial0 is up" part of the show int s0 output tells us that everything is fine physically, but there is a logical problem. 99% of the time with Frame Relay, that's an LMI issue. Let's run show frame lmi twice, a few minutes apart, and see what we can see.
R1#show frame lmi
LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = ANSI
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 121 Num Status msgs Rcvd 94 Num Update Status Rcvd 0 Num Status Timeouts 26
R1#show frame lmi
LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = ANSI
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 134 Num Status msgs Rcvd 94 Num Update Status Rcvd 0 Num Status Timeouts 39
LMI message are still going out, so that's good. The bad part is that the timeout counter is incrementing while the msgs rcvd counter is not. Let's dig a little deeper and run debug frame lmi.
R1#debug frame lmi
Frame Relay LMI debugging is on
Displaying all Frame Relay LMI data
R1#
3d04h: Serial0(out): StEnq, myseq 49, yourseen 94, DTE down 3d04h: datagramstart = 0xE329E4, datagramsize = 14
3d04h: FR encap = 0x00010308
3d04h: 00 75 95 01 01 00 03 02 31 5E
3d04h:
R1#
3d04h: Serial0(out): StEnq, myseq 50, yourseen 94, DTE down 3d04h: datagramstart = 0xE24444, datagramsize = 14
3d04h: FR encap = 0x00010308
3d04h: 00 75 95 01 01 00 03 02 32 5E
3d04h:
R1#
3d04h: Serial0(out): StEnq, myseq 51, yourseen 94, DTE down 3d04h: datagramstart = 0xE24574, datagramsize = 14
3d04h: FR encap = 0x00010308
3d04h: 00 75 95 01 01 00 03 02 33 5E
3d04h:
R1#undebug all
All possible debugging has been turned off
When myseq continues to increment but yourseen is not, that's another indicator of an LMI mismatch. I'll turn the debug back on, change the LMI type back to Cisco, and we'll see the result.
R1#debug frame lmi
Frame Relay LMI debugging is on
Displaying all Frame Relay LMI data
R1#undebug all
All possible debugging has been turned off
As yourseq and yourseen begin to increment, the line protocol comes back up. Once you see that, you should be fine, but always stick around for a minute or so and make sure the line protocol stays up. Once you're done, always do two things....
Verify the line protocol is up with show interface serial. Note that you can see other information relating to the LMI in this output.
R1#show int s0 Serial0 is up, line protocol is up Hardware is HD64570
Internet address is 172.12.123.1/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation FRAME-RELAY, loopback not set
Keepalive set (10 sec)
LMI enq sent 180, LMI stat recvd 114, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 1023 LMI type is CISCO frame relay DTE
And before you leave the client site... turn off your debugs, either individually or with the undebug all command.
R1#undebug all
All possible debugging has been turned off
The LMI isn't the only required match in Frame Relay - the encapsulation type must match as well. We'll take a detailed look at that requirement in our next CCNA / CCENT Exam tutorial!
