This how-to guide will address all those questions and show you how to configure your Frame-Relay switch such as Cisco 2520 or the Cisco 2522 routers to route frame relay packets between your routers.
Any cisco router can serve as a frame-relay switch, but you may want to get one with 4 or more serial ports so you are able to connect many routers to it for a real-world simulation. I recommend that you buy a used cisco 2520 (for a small lab setup) or the cisco 2522 router (for large lab setup).
If you can afford it, you can buy a 2611XM router with 8-port asynchronous/synchronous serial network module (NM-8A/S) or the 16-port asynchronous/synchronous serial network module (NM-16A/S) and run latest IOS for greater scalability and expandability.
2520 and 2522 Comparison
Cisco 2520 has:
- 1 Ethernet port with a selectable attachment unit interface (AUI) connection or 1 Ethernet 10BaseT connection
- 1 Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) port (RJ-45)
- 2 high-speed synchronous serial ports
- 2 low-speed asynchronous/synchronous serial port
However, we will be using the cisco 2522 router for this how-to guide, which has:
- 1 Ethernet/IEEE 802.3 interface(s)
- 2 Serial network interface(s)
- 8 Low-speed serial(sync/async) network interface(s)
- 1 ISDN Basic Rate interface(s)
Other equipment being used which made this how-to possible:
- Cisco 2611XM (R1, R2, R3 and R4)
Dual Fast Ethernet Interfaces
2 WAN Interface Card (WIC) Slots with WIC-1T cards (installed)
1 NM Slot - Cisco 2511 Access Server
1 Ethernet
2 synchronous serial ports
16 asynchronous serial ports
The Network Topology in this scenario, a fully-meshed network:
The routers are connected with the frame-relay switch using DB-60 to DB-60 DTE/DCE cables, with DCE end of the cables attached to the frame-relay switch.
Let's log on to our frame relay switch and start configuring it
Before you can do any frame-relay switching on this router, you must enable it using this command:
FrameRelay-2522(config)# frame-relay switching
Enter the serial interface configuration mode:
FrameRelay-2522(config)# interface serial1
Add the description command so you know which interface is connected to which router:
FrameRelay-2522(config-if)#description Connected to Router1's Serial0 Interface
The interface should not have any IP address, so remove it with this command:
FrameRelay-2522(config-if)# no ip address
Encapsulation must be set to frame-relay, so use this command to set that:
FrameRelay-2522(config-if)# encapsulation frame-relay
FrameRelay-2522(config-if)# clock rate 64000
Set the Local Management Interface (LMI) type to ANSI:
FrameRelay-2522(config-if)# frame-relay lmi-type ansi
Set the frame-relay switch's interface type as DCE:
FrameRelay-2522(config-if)# frame-relay intf-type dce
Turn the interface on, enable it using:
FrameRelay-2522(config-if)# no shutdown
Let's configure the DLCI mapping:
FrameRelay-2522(config-if)# frame-relay route 102 interface Serial2 201
The above command will route packets with input DLCI of 102 to output interface of serial2 with output DLCI of 201. This will allow the frame relay switch to route packets between router1 (R1)'s serial0 to router2 (R2)'s serial0 interfaces.
Confused? Let's do another one on the same interface:
FrameRelay-2522(config-if)# frame-relay route 103 interface Serial2 301
That enables communication between Router1 (R1) and Router3 (R3) through the frame-relay switch.
Study the attached topology diagram to understand this better.
You will need to repeat these commands on each interface of the frame-relay switch along with correct DLCI mappings.
Let's verify the configuration on the frame-relay switch and circuit status. Since our routers were already configured with frame relay and DLCI mappings, they should be talking to each other. Let's take a look with following command:
Frame-Relay-2522# show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DCE)
<
DLCI = 102, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial1
input pkts 1581 output pkts 1560 in bytes 305706
out bytes 367148 dropped pkts 1 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 Num Pkts Switched 1581
pvc create time 13:23:39, last time pvc status changed 12:36:58
DLCI = 103, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial3
input pkts 38 output pkts 66 in bytes 5082
out bytes 7734 dropped pkts 1 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 Num Pkts Switched 37
pvc create time 13:23:49, last time pvc status changed 12:43:19
Notice the bold text, PVC status = ACTIVE means that the circuit is up and routers are communicating.
Let's run another command to verify our configuration:
Frame-Relay-2522# show frame-relay route
| Input Intf | Input Dlci | Output Intf | Output Dlci | Status |
| Serial1 | 102 | Serial1 | 201 | active |
| Serial2 | 103 | Serial1 | 301 | active |
| | | | | |
The above output shows you the mappings we performed earlier. If anything that says "inactive" in the status then there is a problem either on the corresponding routers or the frame relay configuration.
Finally, one more command to further check to make sure that everything is in working order:
Frame-Relay-2522# show frame-relay lmi
LMI Statistics for interface Serial1 (Frame Relay DCE) 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. Rcvd 4625 Num Status msgs Sent 4625
Num Update Status Sent 0 Num St Enq. Timeouts 78
LMI Statistics for interface Serial2 (Frame Relay DCE) 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. Rcvd 4624 Num Status msgs Sent 4624
Num Update Status Sent 0 Num St Enq. Timeouts 75
The number in the bold text should be increasing/changing every time you run the command.
Thats it, we are done with the basic configuration of the frame relay switch. If you have any questions or comments, feel free to post them here or use the contact us link to submit your feedback.
Good luck!
