Back-to-Back Frame Relay Configurations

Introduction:

The following document describes how to configure back-to-back Frame Relay.  Two configurations are shown below.  The first configuration between R1 and R3 will not use LMI and the second configuration between R2 and R3 will use LMI.

Topology:

Configuration:

When configuring back-to-back Frame Relay without LMI, the no keepalive command will be needed on the physical interface of both routers.   Note that the DLCI status in this case with be "Static" as opposed to the normal "Active".

When configuring back-to-back Frame Relay with LMI, one router will need to have the global command frame-relay switching enabled along with the interface level frame-relay intf-type dce command.   In this example R3 has these commanded configured.   Note that these commands are in no way related to the clock rate command on the router with the DCE side of the serial cable.

R1:

interface Serial0/1
 encapsulation frame-relay
 no keepalive
!
interface Serial0/1.1 point-to-point
 ip address 10.13.13.1 255.255.255.0
 frame-relay interface-dlci 131 

R2:

interface Serial0/1
 encapsulation frame-relay
!
interface Serial0/1.1 point-to-point
 ip address 10.23.23.2 255.255.255.0
 frame-relay interface-dlci 232 

R3:

frame-relay switching
!
interface Serial1/2
 encapsulation frame-relay
 no keepalive
 clockrate 64000
!
interface Serial1/2.1 point-to-point
 ip address 10.13.13.3 255.255.255.0
 frame-relay interface-dlci 131
!
interface Serial1/3
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
!
interface Serial1/3.1 point-to-point
 ip address 10.23.23.3 255.255.255.0
 frame-relay interface-dlci 232  

Verification for R1 to R3:

Rack1R1#show frame-relay pvc 131
PVC Statistics for interface Serial0/1 (Frame Relay DTE)

DLCI = 131, DLCI USAGE = LOCAL, PVC STATUS = STATIC, INTERFACE = Serial0/1.1

  input pkts 37            output pkts 40           in bytes 5774
  out bytes 7076           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 12        out bcast bytes 4164
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  pvc create time 00:12:31, last time pvc status changed 00:12:05
Rack1R1#show frame-relay lmi

Rack1R1#ping 10.13.13.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.13.13.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/30/32 ms
Rack1R1#

Verification for R2 to R3:

Rack1R2#show frame-relay pvc 232

DLCI = 232, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/1.1

  input pkts 17            output pkts 17           in bytes 4336
  out bytes 4684           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 12        out bcast bytes 4164
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  pvc create time 00:12:52, last time pvc status changed 00:12:41
Rack1R2#show frame-relay lmi

LMI Statistics for interface Serial0/1 (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 78               Num Status msgs Rcvd 79
  Num Update Status Rcvd 0              Num Status Timeouts 0
Rack1R2#ping 10.23.23.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.23.23.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/30/32 ms
Rack1R2#

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