e this method because it shows that you've assigned the DLCI to the subinterface and that you've mapped it to an IP address. If you just use the map statement, it doesn't seem as obvious. Still, either way is acceptable. On point-to-point subinterfaces, you don't really need to map IP addresses to DLCIs, as the router will know that the far end is the only other IP address available (assuming a network mask of 255.255.255.252). Remember that if you make point-to-point links with subinterfaces, each PVC will now require its own IP network. Figure 23-12 shows the same network as Figure 23-11, only this time with each of the PVCs assigned to specific Frame Relay subinterfaces. Routers B and C don't technically need subinterfaces in this scenario, but if you con- figured them on the physical interface, you need to change the configuration if you later added a PVC between Routers B and C. Configuring the subinterfaces now will po- tentially make life easier in the future. Here are the configurations for the three routers: Router A: interface Serialo/o no ip address encapsulation frame-relay interface Serial0/0.102 point-to-point ip address 192.168.1.1 255.255.255.252 frame-relay interface-dlci 102 protocol ip 192.168.1.2 interface Serial0/0.103 point-to-point ip address 192.168.2.1 255.255.255.252 frame-relay interface-dlci 103 protocol ip 192.168.2.2 Chapter 23: Frame Relay Router B 192.168.1.2/30 DLCI 201 SO/0.201 192.168.1.1/30 S0/0.102 Router A DLCI 102 DLCI 103 S0/0.103 192.168.2.1/30 S0/0.301 DLCI 301 192.168.2.2/30 Router C Figure 23-12. Three-node Frame Relay network with subinterfaces Router B: interface Serialo/o no ip address encapsulation frame-relay interface Serial0/0.201 point-to-point ip address 192.168.1.2 255.255.255.252 frame-relay interface-dlci 201 protocol ip 192.168.1.1 Router C: interface Serialo/o no ip address encapsulation frame-relay interface Serial0/0.301 point-to-point ip address 192.168.2.2 255.255.255.252 frame-relay interface-dlci 301 protocol ip 192.168.2.1 Troubleshooting Frame Rela