Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model.
Configuring a router as frame relay switch
You may be asked to configure a router as a frame relay switch in CCIE lab exam.
There are 3 types of interfaces in frame relay.
- DTE interface - Default interface type on router to be connected to frame relay switch.
- DCE interface – Interface type on frame relay switch to be connected to router.
- NNI interface – Interface type on frame relay switch in order to connect to another frame relay switch.
Configuration on Frame Relay switch
interface Serial0/0
description To R3
no ip address
encapsulation frame-relay
serial restart-delay 0
frame-relay intf-type dce
frame-relay route 301 interface Serial0/1 103
!
interface Serial0/1
description To R1
no ip address
encapsulation frame-relay
frame-relay intf-type dce
frame-relay route 102 interface Serial0/2 201
frame-relay route 103 interface Serial0/0 301
!
interface Serial0/2
description To R2
no ip address
encapsulation frame-relay
serial restart-delay 0
frame-relay intf-type dce
frame-relay route 201 interface Serial0/1 102
Every packet entering the switch through the interface serial0/1 with DLCI 102 will be switched to interface serial0/2 with DLCI 201 and vice versa. Every packet entering the switch through the interface serial 0/1 with DLCI 103 will be switched to interface serial0/0 with DLCI 301 and viceversa.
Note: You need to configure the frame-relay route command on both incoming and outgoing interface.
Configuration on R1
interface Serial0/0
ip address 20.20.20.1 255.255.255.0
encapsulation frame-relay
frame-relay map ip 20.20.20.2 102 broadcast
frame-relay map ip 20.20.20.3 103 broadcast
end
Configuration on R2
interface Serial0/0
ip address 20.20.20.2 255.255.255.0
encapsulation frame-relay
frame-relay map ip 20.20.20.1 201 broadcast
end
Configuration on R3
interface Serial0/0
ip address 20.20.20.3 255.255.255.0
encapsulation frame-relay
cdp enable
frame-relay map ip 20.20.20.1 301 broadcast
end
Now Let us check on R1
Verify the configuration on the frame relay switch.
Learn the commands
Router(config-if)#encapsulation frame-relay : Turns on Frame Relay encapsulation with the default encapsulation type of cisco.
Router(config-if)#frame-relay lmitype {ansi | cisco | q933a} : Depending on the option you select, this command sets the LMI type to the ANSI standard, the Cisco standard, or the ITU-T Q.933 Annex A standard.
Router(config-if)#frame-relay interface-dlci 110 : Sets the DLCI number of 110 on the local interface and enters Frame Relay DLCI configuration mode.
Router(config-if)#frame-relay map ip 20.20.20.2 102 broadcast : Maps the remote IP address (20.20.20.2) to the local DLCI number (102). The optional broadcast keyword specifies that broadcasts across IP should be forwarded to this address. This is necessary when using dynamic routing protocols.
Router(config-if)#no frame-relay inverse arp : Turns off Inverse ARP.
Router#show frame-relay map : Displays IP/DLCI map entries.
Router#show frame-relay pvc : Displays the status of all PVCs configured.
Router#show frame-relay lmi : Displays LMI statistics.
Router#clear frame-relay counters : Clears and resets all Frame Relay counters.
Router#clear frame-relay inarp : Clears all Inverse ARP entries from the map table.
Related Topics : Frame Relay Technology Frame Relay Interface Types