Part 3: Frame Relay Switching

A Router, by default is DTE devices, it can be configured as a Frame Relay Switch by changing the interface to a DCE. Frame Relay Switch will forward Frame Relay frames based on upon their DLCI numbers. Let's see the Logical Frame Relay network below.

Logical Frame Relay Network

Frame Relay Cloud can be one or a group of Frame Relay switch or a router configured as Frame Relay switch. On the network topology below, we'll see the router functioned as Frame Relay switch.

Physical Frame Relay Network

To configure router acts as Frame Relay switch, use the following steps below :

1. Enable frame-relay switching on the global configuration
2. Change the serial interface type to DCE using command frame-relay intf-type dce
3. Create DLCI forwarding rules using command frame-relay route
4. Activate clockrate command. It will provide clocking signal to the attached DTE devices.

Here the complete configuration Frame Relay network above:

R1

 !
 hostname R1
 !  
 interface Serial1/0  
  ip address 10.1.1.1 255.255.255.0  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay interface-dlci 102  
  frame-relay interface-dlci 103  
 !  

R2

 !
 hostname R2
 !  
 interface Serial1/0  
  ip address 10.1.1.2 255.255.255.0  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay interface-dlci 201  
  frame-relay interface-dlci 203  
 end  

R3:

 !
 hostname R3
 !  
 interface Serial1/0  
  ip address 10.1.1.3 255.255.255.0  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay interface-dlci 301  
  frame-relay interface-dlci 302  
 end  

FR

!
hostname FR
!
frame-relay switching
!
interface Serial1/0  
  description to R1  
  no ip address  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay intf-type dce  
  frame-relay route 102 interface Serial1/1 201  
  frame-relay route 103 interface Serial1/2 301  
 !  
 interface Serial1/1  
  description to R2  
  no ip address  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay intf-type dce  
  frame-relay route 201 interface Serial1/0 102  
  frame-relay route 203 interface Serial1/2 302  
 !  
 interface Serial1/2  
  description to R3  
  no ip address  
  encapsulation frame-relay  
  serial restart-delay 0  
  frame-relay intf-type dce  
  frame-relay route 301 interface Serial1/0 103  
  frame-relay route 302 interface Serial1/1 203  
 !  

Verify configuration

R1

 R1#show frame-relay map  
 Serial1/0 (up): ip 10.1.1.2 dlci 102(0x66,0x1860), dynamic,  
        broadcast,, status defined, active  
 Serial1/0 (up): ip 10.1.1.3 dlci 103(0x67,0x1870), dynamic,  
        broadcast,, status defined, active  

 R1#show frame-relay lmi  
 LMI Statistics for interface Serial1/0 (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 402       Num Status msgs Rcvd 393  
  Num Update Status Rcvd 0       Num Status Timeouts 9  
  Last Full Status Req 00:00:27     Last Full Status Rcvd 00:00:27  

R1#show frame-relay pvc

PVC Statistics for interface Serial1/0 (Frame Relay DTE)

              Active     Inactive      Deleted       Static
  Local          2            0            0            0
  Switched       0            0            0            0
  Unused         0            0            0            0

DLCI = 102, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/0

  input pkts 16            output pkts 14           in bytes 1244
  out bytes 1176           dropped pkts 0           in pkts dropped 0
  out pkts dropped 0                out bytes dropped 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 4         out bcast bytes 136
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  pvc create time 01:07:10, last time pvc status changed 01:04:01

DLCI = 103, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/0

  input pkts 15            output pkts 14           in bytes 1210
  out bytes 1176           dropped pkts 0           in pkts dropped 0
  out pkts dropped 0                out bytes dropped 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 01:09:30, last time pvc status changed 01:04:00

FR

 FR#show frame-relay route  
 Input Intf   Input Dlci   Output Intf   Output Dlci   Status  
 Serial1/0    102       Serial1/1    201       active  
 Serial1/0    103       Serial1/2    301       active  
 Serial1/1    201       Serial1/0    102       active  
 Serial1/1    203       Serial1/2    302       active  
 Serial1/2    301       Serial1/0    103       active  
 Serial1/2    302       Serial1/1    203       active  

Test configuration using Ping

R1

R1#ping 10.1.1.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/28/44 ms
R1#ping 10.1.1.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/25/40 ms

R2

R2#ping 10.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/18/32 ms
R2#ping 10.1.1.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/24 ms