Operation Manual – ARPH3C S5500-EI Series Ethernet Switches Chapter 1 ARP Configuration1-3Figure 1-2 ARP address resolution processWhen Host A and Host B are not on the same subnet, Host A first sends an ARPrequest to the gateway. The destination IP address in the ARP request is the IP addressof the gateway. After obtaining the MAC address of the gateway from an ARP reply,Host A encapsulates the packet and sends it to the gateway. Subsequently, thegateway broadcasts the ARP request, in which the destination IP address is the one ofHost B. After obtaining the MAC address of Host B from another ARP reply, thegateway sends the packet to Host B.1.1.4 ARP Mapping TableAfter obtaining the destination MAC address, the device adds the IP-to-MAC mappinginto its own ARP mapping table. This mapping is used for forwarding packets with thesame destination in future.An ARP mapping table contains ARP entries, which fall into two categories: dynamicand static.1) A dynamic entry is automatically created and maintained by ARP. It can get aged,be updated by a new ARP packet, or be overwritten by a static ARP entry. Whenthe aging timer expires or the port goes down, the corresponding dynamic ARPentry will be removed.2) A static ARP entry is manually configured and maintained. It cannot get aged or beoverwritten by a dynamic ARP entry. It can be permanent or non-permanent.z A permanent static ARP entry can be directly used to forward packets. Whenconfiguring a permanent static ARP entry, you must configure a VLAN andoutbound port for the entry besides the IP address and MAC address.z A non-permanent static ARP entry cannot be directly used for forwarding data.When configuring a non-permanent static ARP entry, you only need to configurethe IP address and MAC address. When forwarding IP packets, the device sendsan ARP request. If the source IP and MAC addresses in the received ARP replyare the same as the configured IP and MAC addresses, the device adds the port
