Inverse ARP

Inverse ARP (Address Resolution Protocol) is a protocol used by Frame Relay networks to obtain the IP addresses of other devices on the same network. Inverse ARP allows a router to map a Frame Relay DLCI (Data Link Connection Identifier) to the IP address of a connected device.

When a Frame Relay connection is established between two devices, the Frame Relay network assigns a unique DLCI to each connection. Inverse ARP is used to map these DLCIs to the corresponding IP addresses of the devices on either end of the connection. This mapping is used by the router to forward packets to the correct destination.

Inverse ARP works by using an LMI (Local Management Interface) message to request the IP address associated with a specific DLCI. The device on the other end of the Frame Relay connection responds with an LMI message that contains the IP address. The router then uses this information to create a mapping between the DLCI and IP address.

Inverse ARP can be enabled or disabled on a Frame Relay connection. By default, Inverse ARP is enabled on Cisco routers. Inverse ARP can be useful in simplifying Frame Relay network configurations and reducing administrative overhead. However, it is important to ensure that only valid mappings are created to prevent unauthorized access to the network.