Address Resolution Protocol (ARP) – Is a broadcast message that resolve the Mac address for a know IP Address. You can’t arp to different network, To able to ARP you must be in the same network to get the mac address.
1. ARP – IP Address to Mac Address
2. Reverse Arp – Mac Address to IP Address
3. Inverse Arp – Used in frame relay to learn dlci value
4. Proxy Arp – It gives the virtual mac to reach the destination.
5. Gratious Arp – according to me, this is used in AVG(active virtual gateway) in GLBP. Gratious ARP is used to find out any IP Address duplication. Gratuitous arp use to update other device arp table when a device recivees an arp request with an ip that it’s already in it cache and after that the cache will be updateed with the new information.