Using Proxyarp protects the network structure, hide a network, allows the host to interwork with the current network without modifying the IP address and subnet mask. Example: If a company, it was originally only used with a 2-layer switch, and there was only one subnet 192.168.0.0.0/24, and because of the sequential division, the address is 192.168.0.127. When the company's machine is increased, you need to divide the network segment into 2 subnets 192.168.0.0/25 and 192.168.0.128/25, and the two network segments are connected with the router. At this time, the network management is concerned that the newly purchased machine is drawn directly in the subnet of 192.168.0.128/25, and the port IP of the router is connected to 192.168.0.254, and as the default gateway of the PC in the new subnet . The old PC still maintains the setting of 192.168.0.0.0/24, but the address is 127, and the gateway is not set. Set the interface connected to the old network segment to Proxy ARP, and set the address 192.168.0.126 mask 255.255.255.128, that is, the router interface is configured as specified. When a certain time, it is in the first old subnet, such as 192.168.0.1, thinking and 192.168.0.250 communication, because its mask is 24 bits, so it thinks 192.168.0.250 is a network segment with yourself, so Will send ARP queries directly. Since the proxy ARP is used in the router interface connected to the old network segment, it will respond with its own MAC address. 192.168.0.1 Those the MAC address is the MAC address of 192.168.0.250, so this MAC address is used as the destination MAC address of the Ethernet frame to send the packet. So this packet will be sent to the router, then the router is forwarded to 192.168.0.250. The packet returned from 192.168.0.250, first to the router, then the router is forwarded to 192.168.0.1, and the communication process is completed.
Set the gateway in the MS system: 1. No gateway ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. The address is added to the package 2. The gateway is set to themselves .................................................................. Set as a router address ................ Ordinary mode, PC ARP interpret the router address, then cross-network segment data packet transfire 4. The gateway is set to unused this network segment address .... Ordinary mode, PC ARP interprets the router address, failed, unable to across network segments 5. The gateway is set to non-this segment address ......................... ARP request, router response
