ZyXEL Communications GS-1524 User Manual

GS-1524/GS-1548 User’s Guide

This chapter describes how to activate dynamic Address Resolution Protocol (ARP) learning 
and how to enter static ARP table entries.

Address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP 
address) to a physical machine address, also known as a Media Access Control or MAC 
address, on the local area network. 
An IP (version 4) address is 32 bits long. In an Ethernet LAN, MAC addresses are 48 bits 
long. The ARP table maintains an association between each MAC address and its 
corresponding IP address. 

The ARP table is populated with MAC and corresponding IP address mappings in two 
different ways.

• DHCP Snooping - The Switch listens to traffic from a DHCP server on a trusted port and 

learns IP-to-MAC address bindings by parsing DHCP ACK packets. 

• Static Entries - The Switch administrator can enter static IP-to-MAC address mappings 

via the web configurator.

When an incoming ARP packet destined for a host device on a local area network arrives at 
the Switch, the Switch's ARP program looks in the ARP table and, if it finds the address, sends 
it to the device.
If no entry is found for the IP address, dynamic ARP discards the ARP packet.

Click Dynamic ARP > Settings in the navigation panel to open the following screen. Use the 
Dynamic ARP screen to configure ARP filtering on the specified VLANs.