Frame relay interfaces can be configured as Physical, Multipoint and point-to-point interfaces. Frame relay routing protocols and mostly all network configurations are heavily affected by interface type selected.
In the following diagram R1 is connected to R2 using frame-relay and we are going to explore different configuration options.
Task1: Configure frame-relay PVC between R1 and R2 using Physical interfaces are considered to be multipoint interfaces by default, which means that address resolution is essential in order for both ends to communicate. Address resolution can be accomplished manually using the frame-relay map command or dynamically using inverse ARP.
Dynamic address resolution using InArp:
R1 configuration:
R1(config-if)#encapsulation frame-relay
R1(config-if)#frame-relay inverse-arp
R1(config-if)#ip address 10.10.12.1 255.255.255.0
R1(config-if)#no shut
R2 configuration:
R2(config)#int s1/0
R2(config-if)#encapsulation frame-relay
R2(config-if)#frame-relay inverse-arp
R2(config-if)#ip address 10.10.12.2 255.255.255.0
R2(config-if)#no shut
Configuration Notes:
Configuration Notes:
DLCI is automatically received from the frame-relay switch and assigned to the physical interface by default. We don’t need to make any special configuration for DLCIs when using physical interfaces. Frame relay address resolution is accomplished dynamically using inverse ARP as shown in the following command's output.
Verification and troubleshooting:
R1#ping 10.10.12.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.12.2, timeout is 2 seconds:
!!!!!
The success rate is 100 percent (5/5), round-trip min/Avg/max = 40/112/232 ms
R1#sh frame-relay map
Serial1/0 (up): IP 10.10.12.2 dlci 102 (0×66,0×1860), dynamic, Broadcast, CISCO, status defined, active
R2#ping 10.10.12.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.12.1, timeout is 2 seconds:
!!!!!
The success rate is 100 percent (5/5), round-trip min/Avg/max = 28/114/288 ms
R2#sh frame-relay map
Serial1/0 (up): IP 10.10.12.1 dlci 201 (0xC9,0×3090), dynamic,
Broadcast,
CISCO, status defined, active
Manual address resolution:
If Inverse ARP requests are disabled, address resolution must be configured manually using the frame-relay map command.
R1(config)#int s1/0
R1(config-if)#no frame-relay inverse-arp
R1(config-if)#frame-relay map ip 10.10.12.2 102 broadcast
R2(config)#int s1/0
R2(config-if)#no frame-relay inverse-arp
R2(config-if)#frame-relay map ip 10.10.12.1 201 broadcast
The broadcast keyword is optional but recommended as it allows broadcast and multicast traffic to traverse the PVC.
Verification and troubleshooting:
R1#ping 10.10.12.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.12.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/155/376 ms
R1#sh frame-relay map
Serial1/0 (up): ip 10.10.12.2 dlci 102(0×66,0×1860), static,
broadcast,
CISCO, status defined, active
R2#ping 10.10.12.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.12.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/101/248 ms
R2#sh frame-relay map
Serial1/0 (up): ip 10.10.12.1 dlci 201(0xC9,0×3090), static,
broadcast,
CISCO, status defined, active
Task2: configure the frame-relay connection between R1 and R2 using multipoint sub interfaces:
Dynamic address resolution:
R1(config-subif)#int s1/0
R1(config-if)#encapsulation frame-relay
R1(config-if)#int s1/0.21 multipoint
R1(config-subif)#ip address 10.10.12.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 102
R2(config)#int s1/0
R2(config-if)#encapsulation frame-relay
R2(config-if)#int s1/0.21 multipoint
R2(config-subif)#ip address 10.10.12.2 255.255.255.0
R2(config-subif)#frame-relay interface-dlci 201
Verification and Troubleshooting:
R1#sh frame-relay map
Serial1/0.21 (up): ip 10.10.12.2 dlci 102(0×66,0×1860), dynamic,
broadcast,, status defined, active
R2#sh frame-relay map
Serial1/0.21 (up): ip 10.10.12.1 dlci 201(0xC9,0×3090), dynamic,
broadcast,, status defined, active
Manual address resolution:
R1(config-subif)#int s1/0.21
R1(config-subif)#frame-relay map ip 10.10.12.2 102 broadcast
R2(config-subif)#int s1/0.21
R2(config-subif)#frame-relay map ip 10.10.12.1 201 broadcast
R1#show frame-relay map
Serial1/0.21 (up): ip 10.10.12.2 dlci 102(0×66,0×1860), static,
broadcast,
CISCO, status defined, active
R2#sh frame-relay map
Serial1/0.21 (up): ip 10.10.12.1 dlci 201(0xC9,0×3090), static,
broadcast,
CISCO, status defined, active
Task3: Configure frame-relay connection between R1 & R2 using point-to-point Subinterfaces.
Point-to-Point interfaces do not need any kind of address resolution, only the DLCI must be assigned to the subinterface using the frame-relay interface-dlci command.
R1(config)#int s1/0
R1(config-if)#encapsulation frame-relay
R1(config-if)#int s1/0.12 point-to-point
R1(config-subif)#ip address 10.10.12.1 255.255.255.0
R1(config-subif)#frame-relay interface-dlci 102
R2(config)#int s1/0
R2(config-if)#encapsulation frame-relay
R2(config-if)#int s1/0.12 point-to-point
R2(config-subif)#ip address 10.10.12.2
R2(config-subif)#frame-relay interface-dlci 201
Verification and Troubleshooting:
R1#sh frame-relay map
Serial1/0.12 (up): point-to-point dlci, dlci 102(0×66,0×1860), broadcast
Status defined, active
R2#sh frame-relay map
Serial1/0.12 (up): point-to-point dlci, dlci 201(0xC9,0×3090), broadcast
Status defined, active
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