Inverse Address Resolution Protocol (ARP) is used to dynamically create permanent virtual circuits (PVCs). A PVC is a virtual connection between a source and a destination through which data is transmitted as if over a physical connection. The destination becomes the next hop from the source over the PVC.
PVCs that are created dynamically by Inverse ARP are marked as dynamic in the output of the show frame-relay map command. The show frame-relay map command can be used to verify the local datalink connection identifier (DLCI) numbers that have been assigned to remote IP addresses, the status of the PVC, the encapsulation format that is used by the PVC, and whether the PVC was manually configured or created dynamically.
Inverse ARP is used to find a Layer 3 address when the Layer 2 address is known. In the case of Frame Relay, Inverse ARP maps Layer 2 DLCIs to Layer 3 IP addresses. DLCIs uniquely identify a PVC connection in a Frame Relay circuit.
ARP is not used to dynamically create PVCs. ARP is used to find a Layer 2 address when the Layer 3 address is known. Because Inverse ARP is an extension of ARP, ARP packets are structured the same as Inverse ARP packets.
Reverse ARP (RARP) is not used to dynamically create PVCs. A device uses RARP to obtain an IP address for itself based on its Layer 2 Media Access Control (MAC) address. RARP has the same packet structure as ARP and Inverse ARP. However, RARP has been largely replaced with Dynamic Host Configuration Protocol (DHCP).
DHCP is not used to dynamically create PVCs. DHCP dynamically assigns network configuration information to client computers. This network configuration information can include the IP address, subnet mask, default gateway, and Domain Name System (DNS) servers that the client computer will use.