Four typical scenarios of ARP

Four typical scenarios of ARP: 1. the sender is a host and sends IP packets to another host on the network. Then, use ARP to find the hardware MAC address of the target host. Www.2cto.com 2. the sender is a host, and the IP datagram should be sent to another host on the network. In this case, ARP is used to find the hardware MAC address of a vro (GATEWAY) on the current network. The router is responsible for the remaining work. 3. the sender is a vro and forwards the IP datagram to a host on the network. In this case, use ARP to find the hardware MAC address of the target host. 4. The sender is a router, and the IP datagram must be forwarded to one host in another network. Then, use ARP to find the hardware address of a router (GATEWAY) on the network. The remaining work is completed by this router. The behavior of a host and a vro is the same. The difference is that a vro can act as a gateway, but a PC cannot. When forwarding an IP datagram to a host in another network, ARP finds the hardware MAC address of a gateway on the network. The Gateway can be a router or a layer-3 switch. Www.2cto.com pure L2 switches do not have ARP entries. Whether the switch has an ARP table depends on whether the switch is used as a layer-3 device (with a layer-3 router interface or SVI interface). However, when a data frame is transmitted on the link of the actual network, the hardware address of the network must be used. Each host has an ARP high-speed cache, which contains a ing table between IP addresses of hosts and gateways on the local LAN to hardware addresses. That is to say, a host can be connected to other hosts in the local area network through ARP, and the work of arriving at other network hosts is handed over to the gateway. The mac address of the same subnet source object does not change the IP address of the different subnet source object, but does not change the MAC address of the source object.