Default Routers

As discussed in some detail back in Chapter 16, “Configuring IPv4 Addresses and Routes,” IPv4 host routing logic reduces to a basic two-part choice. For packets destined for a host in the same subnet, the local host sends the packet directly, ignoring any routers. For packets destined for a host in a different subnet, the local host next sends the packet to its default gateway (also known as the default router), expecting that router to forward the packet.

Interestingly, a couple of simple errors can occur between any LAN-based host and their default router. For a LAN-based host’s default router setting to work, the following must be true:

The host link to the LAN and the default router link to the LAN must be in the same VLAN. ...

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