How does IP router deliver IP packets to an IP host?
First we need to realize that IP router is a computer (host), which has multiple network adapters, each associated with a different IP address. These network adapters enable the router to be a physical member of multiple subnets (e.g. LANs), thus enabling it to forward IP packets from one subnet to another. You can think of a router as an electronic version of an octopus, each one of its legs is connected (“belongs”) to a different subnet… Upon receipt of an IP packet, the IP router takes a look at the IP portion (header) of the packet (datagram). In particular it examines the destination IP address field in the IP header. It looks up its routing table (using the destination IP address as a key) and finds the closets matching entry. This entry tells the router what is the next hop to go to, and via which network adapter (AKA interface) to do so. The next hop could be as simple as a host on the neighbor subnet, which its IP address is the one indicated in the IP packet (and thus is th
