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.
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:
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
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:
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.