IPv4 Host Routing
Hosts actually use some simple routing logic when choosing where to send a packet. If you assume that the design uses subnets (which is typical), this two-step logic is as follows:
Step 1. If the destination IP address is in the same IP subnet as I am, send the packet directly to that destination host.
Step 2. Otherwise, send the packet to my default gateway, also known as a default router. (This router has an interface on the same subnet as the host.)
For example, consider Figure 4-10 and focus on the Ethernet LAN on the left. When PC1 sends an IP packet to PC11 (150.9.1.11), PC1 first considers some match related to subnetting. ...
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