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Cisco Frame Relay Configurations

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Apr 30, 2004.

Chapter Description

Jonathan Chin dicussess basic Frame Relay operations on Cisco routers in a router-based Frame Relay network. He also explains how to configure a basic frame relay network involving Cisco equipment and how to perform basic monitoring and troubleshooting using relevant Cisco IOS show and debug commands.

Verifying Frame Relay Connections with IOS show Commands

Many Cisco IOS commands that are supported on Cisco routers can be used either to validate users' Frame Relay configuration command changes, to verify the status of the Frame Relay connection, or as a troubleshooting tool. For instance, the show frame-relay map command displays the remote network address to local DLCI mapping and indicates the remote network destinations reachable via the connected Frame Relay network. This section looks at the general IOS show commands most commonly used on Cisco routers for Frame Relay.

show interface serial interface-type number

The show interface serial privileged EXEC mode command displays detailed information of a physical interface or a subinterface. The information shown by the show interface serial command offers the following information on Frame Relay:

  • The type of Frame Relay encapsulation used on an interface or PVC

  • The keepalive interval configured

  • The Frame Relay LMI type used

  • The status of Frame Relay LMI

  • Information on whether the interface is configured as a Frame Relay DTE or a DCE device

Example 4-30 shows a sample output of the show interface serial command. Different hardware interface types might have slightly different output formats.

Example 4-30 Sample Output of show interface serial Command

Router#show interface serial1/2
Serial1/2 is up, line protocol is up 
 Hardware is CD2430 in sync mode
 Internet address is
 MTU 1500 bytes, BW 128 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 131, LMI stat recvd 116, 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
 FR SVC disabled, LAPF state down
 Broadcast queue 0/64, broadcasts sent/dropped 9/0, interface broadcasts 0
 Last input 00:00:03, output 00:00:03, output hang never
 Last clearing of "show interface" counters 00:24:10
 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
 Queueing strategy: fifo
 Output queue :0/40 (size/max)
 5 minute input rate 0 bits/sec, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
   241 packets input, 8933 bytes, 0 no buffer
   Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
   0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
   164 packets output, 2865 bytes, 0 underruns
   0 output errors, 0 collisions, 10 interface resets
   0 output buffer failures, 0 output buffers swapped out
   2 carrier transitions
   DCD=up DSR=up DTR=up RTS=up CTS=up

The output of the show interface serial command offers other beneficial information for verifying the Frame Relay router's connection to the CSU/DSU. When the output of the show interface serial command shows Serial1/2 is up, line protocol is up, this indicates that the router is communicating properly with the connected CSU/DSU and is successfully exchanging LMI status messages with the Frame Relay switch. The line Serial1/2 is down, line protocol is down reveals that a line problem has occurred with the router's connection to the CSU/DSU. The causes of the problem are typically cabling or signaling issues. The last line of the show interface serial command offers information on the status of the interface's connection with the CSU/DSU. When the output shows Serial1/2 is up, line protocol is down, this means that the local connection to the CSU/DSU is functioning properly, but the router is not exchanging LMI messages properly with the switch.

show frame-relay lmi [interface_type interface_number]

The show frame-relay lmi privileged EXEC mode command displays LMI statistics of Frame Relay enabled interfaces on the router. Alternatively, the command can be used to display the LMI statistics of a certain interface by specifying the interface type and the interface number. For example, show frame-relay lmi serial4/2 displays the LMI statistics for the Frame Relay operations configured on serial4/2 only. The information displayed by the show frame-relay lmi command shows the LMI type used by the Frame Relay interface as well as the counters for the LMI status exchange sequence, including errors such as LMI timeouts. Example 4-31 shows a sample output of the show frame-relay lmi command.

Example 4-31 Sample Output of show frame-relay lmi Command

Router#show frame-relay lmi
LMI Statistics for interface Serial1/2 (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 159       Num Status msgs Rcvd 144
 Num Update Status Rcvd 0       Num Status Timeouts 16

show frame-relay map

The show frame-relay map privileged EXEC mode command shows the contents of the next hop protocol address to DLCI mapping table on the router. The table contains both dynamic mapped and static mapped entries. Example 4-32 shows a sample output of the show frame-relay map command.

Example 4-32 Sample Output of show frame-relay map Command

Router#show frame-relay map
Serial1/2 (up): ip dlci 401(0x191,0x6410), dynamic,
       broadcast,, status defined, active
Serial1/2 (up): ip dlci 501(0x1F5,0x7C50), dynamic,
       broadcast,, status defined, active
Serial1/2 (up): ip dlci 301(0x12D,0x48D0), dynamic,
       broadcast,, status defined, active

show frame-relay pvc

The show frame-relay pvc privileged EXEC mode command displays detailed information of the PVC statistics on the router. This is an important command for monitoring Frame Relay connections on the router. It offers information such as all the DLCIs on the router, the interface that a DLCI is associated with, and the status of the PVC, as well as traffic and congestion management parameters such as the number of BECN, FECN, and DE flagged packets received. It also shows the input and output rate information on a per-VC basis.


The format of the show frame-relay pvc output changes slightly and presents more information when certain Frame Relay features are configured on the router.

Example 4-33 shows a sample standard output of the show frame-relay pvc command.

Example 4-33 Sample Output of show frame-relay pvc Command

Router#show frame-relay pvc
PVC Statistics for interface Serial3/0 (Frame Relay DTE)

           Active   Inactive   Deleted    Static
 Local     1        0          0          0
 Switched  0        0          0          0
 Unused    0        0          0          0


 input pkts 12        output pkts 3      in bytes 408    
 out bytes 102        dropped pkts 0      in FECN pkts 0     
 in BECN pkts 0       out FECN pkts 0     out BECN pkts 0     
 in DE pkts 0         out DE pkts 0     
 out bcast pkts 3     out bcast bytes 102    
 5 minute input rate 0 bits/sec, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
 pvc create time 00:23:41, last time pvc status changed 00:23:41

show frame-relay route

The show frame-relay route privileged EXEC mode command is used to monitor the Frame Relay route table on the Cisco router configured as a Frame Relay switch. The Frame Relay switch uses the routes constructed in the table to switch frames from an incoming VC on an interface to an outgoing VC on another interface. The table also shows the current status of the switched VCs. This command is useful only on the router configured as a Frame Relay switch. Example 4-34 shows a sample output of the show frame-relay route command.

Example 4-34 Sample Output of show frame-relay route Command

Router#show frame-relay route
Input Intf   Input Dlci   Output Intf   Output Dlci  Status
Serial1/0    101       Serial4/3    201      active
Serial1/1    101       Serial4/3    301      active
Serial1/7    101       Serial4/3    501      active
Serial4/1    101       Serial4/3    401      active
Serial4/3    201       Serial1/0    101      active
Serial4/3    301       Serial1/1    101      active
Serial4/3    401       Serial4/1    101      active
Serial4/3    501       Serial1/7    101      active

10. Troubleshooting Frame Relay Connections with Cisco IOS debug Commands | Next Section Previous Section

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