Question one: Why Why should cache entries have expired time rather than remain in effect?
1, reference URL:
2) Linux arp mechanism to resolve
2. Answer:
2.1 ARP cache can reduce the amount of broadcast, when the host sends an ARP request to check whether there is a corresponding IP address in the ARP cache entries, the MAC address returned, if present, between, or before initiating a broadcast. This reduces network traffic, thereby improving the efficiency of communication between computers
2.2 host and has been to a different destination host on the network to communicate, but it would have been if the accumulation of a large number of entries, and some entries use after once may never be used, it has not deleted, it will waste a lot of resources
Second problem: If the source and destination hosts not in the same network segment, a broadcast ARP request frame can not pass through the router, the source host and the destination host how to communicate
1. Reference Site
1) Baidu know
2. Answer:
When different network host communications 2.1, encapsulating gateway host (typically a router ) mac address, and then sends the data to the host router , routing forwarding subsequent routing, arp resolve the destination mac address by address, and then send the data packet destination.