Value Description5 Chaos6 IEEE802.X7 ARC networkARP TableIn an Ethernet, the MAC addresses of two hosts must be available for the two hosts to communicatewith each other. Each host in an Ethernet maintains an ARP table, where the latest used IPaddress-to-MAC address mapping entries are stored. S4500 series Ethernet switches provide thedisplay arp command to display the information about ARP mapping entries.ARP entries in an S4500 series Ethernet switch can either be static entries or dynamic entries, asdescribed in Table 36-3.Table 36-3 ARP entriesARP entry Generation Method Maintenance ModeStatic ARP entry Manually configured Manual maintenanceDynamic ARP entry Dynamically generatedARP entries of this type agewith time. The aging period isset by the ARP aging timer.ARP ProcessFigure 36-2 ARP processSender MACaddress00a0-2470-febdTarget IPaddress192.168.1.1Target IPaddress192.168.1.2Host A192. 168.1.10002-6779-0f4cHost B192. 168.1.200a0-2470-febdTarget MACaddress0000-0000-0000Sender IPaddress192 .168.1.1Sender IPaddress192.168.1. 2Sender MACaddressTarget MACaddress0002-6779-0f4c0002-6779-0f4cSuppose that Host A and Host B are on the same subnet and that Host A sends a message to Host B.The resolution process is as follows:1) Host A looks in its ARP mapping table to see whether there is an ARP entry for Host B. If Host Afinds it, Host A uses the MAC address in the entry to encapsulate the IP packet into a data link layerframe and sends the frame to Host B.2) If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an ARP request, inwhich the source IP address and source MAC address are respectively the IP address and MACaddress of Host A and the destination IP address and MAC address are respectively the IPaddress of Host B and an all-zero MAC address. Because the ARP request is sent in broadcast36-3
