Frame Relay Switch Lab#01

| Sunday, June 20th, 2010 | 5 Comments »

In this lab, we’re going to hit two birds with one stone. We’re going to learn how to configure Cisco routers for frame relay, as well as the configuration for the actual frame relay switch. The frame relay switch will be a regular router. In this case, it’s going to be a 3620 router that is configured with a 4-Port Sync Serial Network Module (NM-4T). Displayed below:

NM-4T serial module

We have three routers in this lab:

  1. RTR-1720
  2. RTR-3620
  3. RTR-2501

The two routers that will  be acting as DTE devices will be: RTR-1720 and RTR-2501

The RTR-3620 router will be our frame relay switch. It will also provide the clock rate. Without the DCE side providing the clocking, the links will not come up.

RTR-3620

First we need to enable frame relay switching on the RTR-3620 by issuing this global configuration command:

RTR-3620#config t
RTR-3620(config)#frame-relay switching

It is very straight forward. What we need to do now is jump into each serial interface, and properly configure them as DCE interfaces.

Interface Serial1/0
RTR-3620(config)#int s1/0
RTR-3620(config-if)#no shut
RTR-3620(config-if)#no ip address
RTR-3620(config-if)#encapsulation frame-relay
RTR-3620(config-if)#frame-relay intf-type  dce
RTR-3620(config-if)#clock rate 38400
RTR-3620(config-if)#frame-relay lmi-type cisco
RTR-3620(config-if)#frame-relay route 100 interface serial1/1 101

Interface Serial1/1
RTR-3620(config)#int s1/1
RTR-3620(config-if)#no shut
RTR-3620(config-if)#no ip address
RTR-3620(config-if)#encapsulation frame-relay
RTR-3620(config-if)#frame-relay intf-type dce
RTR-3620(config-if)#clock rate 38400
RTR-3620(config-if)#frame-relay lmi-type cisco
RTR-3620(config-if)#frame-relay route 101 interface serial1/0 100

Before we go onto configuring the DTE devices, let’s go over what we just did.

encapsulation frame-relay – Here we set the encapsulation type to frame-relay.
frame-relay intf-type dce – This is where we actually tell the interface that it is a DCE and not a DTE.
clock rate <speed> – We set the clocking here. Without it, the links won’t come up.
frame-relay lmi-type ansi – The LMI type here is cisco. It needs to be the same as the DTE. Other options are: ansi and q933a
frame-relay route 101 interface serial1/0 100 – This is important. What we’re doing here is telling the interface, if it receives a DLCI of 101 coming in on this interface, switch this packet to and send out to interface serial1/0 with DLCI 100.

  • route 101 – This is the incoming DLCI number.
  • interface serial1/0 – Switch the packet to this interface.
  • 100 – The outgoing packet will have DLCI 100.

RTR-1720

Here we will be configuring RTR-1720 to be a DTE device.

RTR-1720(config-if)#int s1
RTR-1720(config-if)#ip address 192.1.1.1 255.255.255.0
RTR-1720(config-if)#no shut
RTR-1720(config-if)#encapsulation frame-relay
*RTR-1720(config-if)#frame-relay lmi-type ansi
Edit:
RTR-1720(config-if)#frame-relay lmi-type cisco

RTR-2501

Here we will be configuring RTR-1720 to be a DTE device.

RTR-2501(config-if)#int s0
RTR-2501(config-if)#ip address 192.1.1.3 255.255.255.0
RTR-2501(config-if)#no shut
RTR-2501(config-if)#encapsulation frame-relay
*RTR-2501(config-if)#frame-relay lmi-type ansi
Edit: RTR-2501(config-if)#frame-relay lmi-type cisco

*Thanks to Marko Milivojevic CCIE #18427 who pointed out this typo. The correct LMI type should be “cisco” not “ansi”. I had originally went with ansi, then later changed the frame relay switch to cisco and had forgotten to update this command output.

Verification

So now that we have properly configured our DCE and DTE devices. We look into verifying that the configuration was done properly. The first common step is to PING the other IP address of each DTE device.

RTR-1720#ping 192.1.1.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.1.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 96/96/100 ms

RTR-2501#ping 192.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 92/95/96 ms

Obviously if there were a problem, the PING’S would not have been able to go through. The 100% success rate is a good indication that everything was configured correctly on the DTE and DCE side. So now let’s take a  look at some commands on the DCE (frame relay switch itself)

SHOW FRAME PVC

RTR-3620#sh frame-relay pvc

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

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

DLCI = 100, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial1/0

input pkts 12            output pkts 12           in bytes 1104
out bytes 1100           dropped pkts 2           in pkts dropped 2
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 0         out bcast bytes 0
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
switched pkts 11
Detailed packet drop counters:
no out intf 0            out intf down 0          no out PVC 0
in PVC down 0            out PVC down 2           pkt too big 0
shaping Q full 0         pkt above DE 0           policing drop 0
pvc create time 01:09:06, last time pvc status changed 00:07:31

PVC Statistics for interface Serial1/1 (Frame Relay DCE)

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

DLCI = 101, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial1/1

input pkts 12            output pkts 11           in bytes 1100
out bytes 1070           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 0         out bcast bytes 0
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
switched pkts 12
Detailed packet drop counters:
no out intf 0            out intf down 0          no out PVC 0
in PVC down 0            out PVC down 0           pkt too big 0
shaping Q full 0         pkt above DE 0           policing drop 0
pvc create time 01:07:14, last time pvc status changed 00:05:55

Some important stats here are: PVC STATUS = ACTIVE and the input/output packets. Notice that both outputs showed a PVC STATUS of active. And that both outputs showed packets traversing the interface.

SHOW FRAME LMI

RTR-3620#sh frame-relay lmi

LMI Statistics for interface Serial1/0 (Frame Relay DCE) 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. Rcvd 75               Num Status msgs Sent 75
Num Update Status Sent 0              Num St Enq. Timeouts 5

LMI Statistics for interface Serial1/1 (Frame Relay DCE) 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. Rcvd 212              Num Status msgs Sent 212
Num Update Status Sent 0              Num St Enq. Timeouts 2

This command shows the LMI status between the frame relay switch interface and the DTE devices. The LMI Type here confirms CISCO and that the frame relay is indeed acting as a switch.

SHOW FRAME ROUTE

This is a pretty quick way to see the DLCI mappings on your FR switch and its status.

RTR-3620#sh frame route
Input Intf      Input Dlci      Output Intf     Output Dlci     Status
Serial1/0       100             Serial1/1       101             active
Serial1/1       101             Serial1/0       100             active

This concludes our first frame relay lab. What we were able to accomplish were correctly configuring the DTE devices and to turn a Cisco router into a DCE device. (frame relay switch). We then verified the configuration by running some ping tests across our FR switch to confirm proper DLCI setup as well as displaying show commands on the DCE to further validate the FR switch configuration.

Please feel free to add any questions or comments!

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