This article shows how to configure basic frame relay without using inverse ARP.

Basic Frame Relay

We’ll be using the above topology for the configuration. The IP addresses of the routers are 192.168.1.X, where X is the router number.

Configuration Steps

  1. Assign IP address to the serial interface
  2. Configure frame relay encapsulation
  3. Set frame map for each router

Configuration

Lets assign an IP address to the serial interface

R1

R1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#interface serial 0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0

R2

R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#interface serial 0/0
R2(config-if)#ip address 192.168.1.2 255.255.255.0

R3

R3#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#interface serial 0/0
R3(config-if)#ip address 192.168.1.3 255.255.255.0

Now enable frame relay encapsulation on serial interface and disable inverse ARP

R1

R1(config-if)#encapsulation frame-relay
R1(config-if)#no frame-relay inverse-arp

R2

R2(config-if)#encapsulation frame-relay
R2(config-if)#no frame-relay inverse-arp

R3

R3(config-if)#encapsulation frame-relay
R3(config-if)#no frame-relay inverse-arp

Configure frame relay map to associate IP addresses with proper DLCI and no shut the interface

Basic frame map syntax is

frame-relay map ip <Remote IP Address> <Local DLCI>

R1

R1(config-if)#frame-relay map ip 192.168.1.2 102
R1(config-if)#frame-relay map ip 192.168.1.3 103
R1(config-if)#frame-relay map ip 192.168.1.1 103
R1(config-if)#no shutdown

R2

R2(config-if)#frame-relay map ip 192.168.1.1 201
R2(config-if)#frame-relay map ip 192.168.1.2 201
R2(config-if)#frame-relay map ip 192.168.1.3 201
R2(config-if)#no shutdown

R3

R3(config-if)#frame-relay map ip 192.168.1.3 301
R3(config-if)#frame-relay map ip 192.168.1.2 301
R3(config-if)#frame-relay map ip 192.168.1.1 301
R3(config-if)#no shutdown

Here we are adding IP addresses and the DLCI to reach remote routers. Note that spoke routers (R2 and R3) have 201 and 301 DLCI respectively. Hub router (R1) is using 102 and 103 to reach R2 and R3.

By default, frame relay interface cannot ping itself, so we added local IP address to the frame map as well. For example, when R1 pings itself, the router will send ICMP out DLCI 103 and then R3 will send it back to R1.

Verfication

To display frame map

R1#show frame-relay map
Serial0/0 (up): ip 192.168.1.2 dlci 102(0x66,0x1860), static,
              CISCO, status defined, active
Serial0/0 (up): ip 192.168.1.1 dlci 103(0x67,0x1870), static,
              CISCO, status defined, active
Serial0/0 (up): ip 192.168.1.3 dlci 103(0x67,0x1870), static,
              CISCO, status defined, active

Checking end to end connectivity. Lets check R2 to R3

R2#ping 192.168.1.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/28/76 ms
R2#trace
R2#traceroute 192.168.1.3

Type escape sequence to abort.
Tracing the route to 192.168.1.3

  1 192.168.1.1 60 msec 40 msec 52 msec
  2 192.168.1.3 68 msec *  72 msec

The trace route shows that the packet goes from R2 > R1 > R3

 

That’s it for this tutorial. You can also trace route local address to get similar output.