If you configure vlan, you need to configure one-arm routing. If you configure this way, if there are two VLANs, 10 VLAN 20.

Interface fa0/0. 10

Encapsulate dot 1q 10

Ip address192.168.10.1255.255.0.

Interface fa0/0.20

Encapsulate dot 1q 20

Ip address192.168.20.1255.255.0.

Configuring Frame Relay is almost just a different encapsulation type.