Most CCNA exam preps explain Frame-relay from a client’s angle and not from a service provider’s perspective. With such information, most CCNA holders who proceed to getting a job with ISPs find themselves not being able to implement Frame-relay. Yes, the Frame-relay technology is gradually being replaced by MPLS technology but there are many organisations out there still using Frame-relay. So in this piece I will be sharing a complete guide to setting up a frame-relay network, from start to finish.
Objective: the requirement is to configure a frame-relay cloud to connect three offices in a full-mesh topology. The three offices have local area networks which will be represented with loopback addresses. Our objective is to make the local area networks reachable from all locations.
Implementation plan
The frame-relay network is going the configured on point to point mode, using sub-interfaces on routers in all the locations and local area networks in all locations will be advertised using ospf. The addressing scheme will be as shown below:
WAN links
192.168.1.0/30: between R2 and R3. R2=192.168.1.1 R3=192.168.1.2
192.168.1.4/30: between R2 and R4. R2=192.168.1.5 R4=192.168.1.6
192.168.1.8/30: between R3 and R4. R3=192.168.1.9 R4=192.168.1.10
LAN
R2:172.16.40.0/24
R3:172.16.30.0/24
R4:172.16.40.0/24
Configuration
To build a complete frame-relay cloud, we must in addition to taking care of the routers in all offices, assume ISP’s responsibility by provisioning a router which must be configured as a frame-relay switch with Data Link Connection Identifiers (DLCI) to all locations. In this demonstration, R1 will be configure as a frame-relay switch. See below:
Frame-Sw(config-if)#int s0/0
Frame-Sw(config-if)#no ip address
Frame-Sw(config-if)#no shut
Frame-Sw(config-if)#en frame
Frame-Sw(config-if)#clock rate 64000
Frame-Sw(config-if)#frame intf-type dce
Frame-Sw(config-if)#frame route 200 int s0/1 300
Frame-Sw(config-if)#frame route 201 int s0/2 401
Frame-Sw(config-if)#int s0/1
Frame-Sw(config-if)#no ip address
Frame-Sw(config-if)#en frame
Frame-Sw(config-if)#clock rate 64000
Frame-Sw(config-if)#frame intf-type dce
Frame-Sw(config-if)#frame route 300 int s0/0 200
Frame-Sw(config-if)#frame route 301 int s0/2 400
Frame-Sw(config-if)#int s0/2
Frame-Sw(config-if)#no ip address
Frame-Sw(config-if)#en frame
Frame-Sw(config-if)#clock rate 64000
Frame-Sw(config-if)#frame intf-type dce
Frame-Sw(config-if)#frame route 400 int s0/0 301
Frame-Sw(config-if)#frame route 401 int s0/2 201
Next, we set up R2:
R2(config)#int loopback1
R2(config-if)#desc connection to LAN
R2(config-if)#ip add 172.16.20.1 255.255.255.0
R2(config-if)#no shut
R2(config-if)#int s0/0
R2(config-if)#en frame
R2(config-if)#no ip add
R2(config-if)#no shut
R2(config-if)#int s0/0.200 point-to-point
R2(config-subif)#desc frame-interface to R3
R2(config-subif)#ip add 192.168.1.1 255.255.255.252
R2(config-subif)#frame int 200
R2(config-fr-dlci)#exit
R2(config-subif)#exit
R2(config-if)#int s0/0.201 point-to-point
R2(config-subif)#desc frame-interface to R4
R2(config-subif)#ip add 192.168.1.5 255.255.255.252
R2(config-subif)#frame int 201
R2(config-fr-dlci)#exit
On R3
R3(config)#int loopback1
R3(config-if)#desc connection to LAN
R3(config-if)#ip add 172.16.30.1 255.255.255.0
R3(config-if)#no shut
R3(config)#int s0/0
R3(config-if)#en frame
R3(config-if)#no shut
R3(config-if)#no shut
R3(config-if)#no ip add
R3(config-if)#no shut
R3(config-if)#int s0/0.300 point-to-point
R3(config-subif)#desc frame-interface to R2
R3(config-subif)#ip add 192.168.1.2 255.255.255.252
R3(config-subif)#frame int 300
R3(config-fr-dlci)#exit
R3(config-subif)#exit
R3(config-if)#int s0/0.301 point-to-point
R3(config-subif)#desc frame-interface to R4
R3(config-subif)#ip add 192.168.1.9 255.255.255.252
R3(config-subif)#frame int 301
R3(config-fr-dlci)#exit
On R4
R4(config)#int loopback1
R4(config-if)#desc connection to LAN
R4(config-if)#ip add 172.16.40.1 255.255.255.0
R4(config-if)#no shut
R4(config)#int s0/0
R4(config-if)#en frame
R4(config-if)#no ip add
R4(config-if)#no shut
R4(config-if)#no shut
R4(config-if)#int s0/0.400 point-to-point
R4(config-subif)#desc frame-interface to R3
R4(config-subif)#ip add 192.168.1.10 255.255.255.252
R4(config-subif)#frame int 400
R4(config-fr-dlci)#exit
R4(config-subif)#exit
R4(config-if)#int s0/0.401 point-to-point
R4(config-subif)#desc frame-interface to R2
R4(config-subif)#ip add 192.168.1.6 255.255.255.252
R4(config-subif)#frame int 401
R4(config-fr-dlci)#exit
At the point, we have connectivity between locations in the same WAN subnet. Next, is to advertise attached local networks in all locations using ospf. This will ensure reachability across all locations.
Ospf configuration on R2
R2(config)#router ospf 1
R2(config-router)#netw 192.168.1.0 0.0.0.3 area 0
R2(config-router)#netw 192.168.1.4 0.0.0.3 area 0
R2(config-router)#netw 172.16.20.0 0.0.0.255 area 0
Ospf configuration on R3
R3(config)#router ospf 1
R3(config-router)#netw 192.168.1.0 0.0.0.3 area 0
R3(config-router)#netw 192.168.1.8 0.0.0.3 area 0
R3(config-router)#netw 172.16.30.0 0.0.0.255 area 0
Ospf configuration on R4
R4(config)#router ospf 1
R4(config-router)#netw 192.168.1.4 0.0.0.3 area 0
R4(config-router)#netw 192.168.1.8 0.0.0.3 area 0
R4(config-router)#netw 172.16.40.0 0.0.0.255 area 0
R3’s routing table displayed above, shows that we have connectivity to all locations from router 3.