Operation Manual – ARPH3C S5100-SI/EI Series Ethernet Switches Chapter 1 ARP Configuration1-6z With trusted ports configured, ARP packets coming from the trusted ports will notbe checked, while those from other ports will be checked through the DHCPsnooping table or the manually configured IP binding table.z With the ARP restricted forwarding function enabled, ARP request packets areforwarded through trusted ports only; ARP response packets are forwardedaccording to the MAC addresses in the packets, or through trusted ports if theMAC address table contains no such destination MAC addresses.1.1.6 Introduction to Gratuitous ARPThe following are the characteristics of gratuitous ARP packets:z Both source and destination IP addresses carried in a gratuitous ARP packet arethe local addresses, and the source MAC address carried in it is the local MACaddresses.z If a device finds that the IP addresses carried in a received gratuitous packetconflict with those of its own, it returns an ARP response to the sending device tonotify of the IP address conflict.By sending gratuitous ARP packets, a network device can:z Determine whether or not IP address conflicts exist between it and other networkdevices.z Trigger other network devices to update its hardware address stored in theircaches.With the gratuitous ARP packet learning function enabled:A device receiving a gratuitous ARP packet adds the information carried in the packetto its own dynamic ARP table if it finds no corresponding ARP entry for the ARP packetexists in the cache.1.2 Configuring ARP1.2.1 Configuring ARP Basic FunctionsFollow these steps to configure ARP basic functions:To do… Use the command… RemarksEnter system view system-view —Add a static ARP entryarp static ip-addressmac-address [ vlan-idinterface-typeinterface-number ]OptionalBy default, the ARPmapping table is empty,and entries are createddynamically by ARP.Configure the ARP agingtimerarp timer agingaging-timeOptional20 minutes by default.
