TP-Link T1600G-18TS Jetstream Smart Switches User Guide - Page 526

Configuring ARP Overview 1 Overview ARP (Address Resolution Protocol) is used to map IP addresses to MAC addresses. Taking an IP address as input, ARP learns the associated MAC address, and stores the IP-MAC address association in an ARP entry for rapid retrieval. 1.1 Supported Features ARP Table The ARP table displays all the ARP entries, including dynamic entries and static entries. Dynamic Entry: Automatically learned and will be deleted after aging time. Static Entry: Added manually and will be remained unless modified or deleted manually. Static ARP You can manually add ARP entries by specifying the IP addresses and MAC addresses. Gratuitous ARP Gratuitous ARP is a special kind of ARP. Both the source and destination addresses of the gratuitous ARP packet are the sender its own IP address. It is used to detect duplicate IP address. If an interface sends a gratuitous ARP packet and no replies are received, then the sender knows its IP address is not used by other devices. Proxy ARP Normally, the ARP packets can only be transmitted in one broadcast domain, which means if two devices in the same network segment are connected to different Layer 3 interfaces, they cannot communicate with each other because they cannot learn each other's MAC address using ARP packets. Proxy ARP solves this problem. As shown below, when a host sends an ARP request to another device that is not in the same broadcast domain but on the same network segment, the Layer 3 interface with Proxy ARP enabled will respond the ARP request with its own MAC address if the destination IP is reachable. After that, the ARP request sender sends packets to the switch, and the switch forwards the packets to the intended device. User Guide 501