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Sams Teach Yourself Network Troubleshooting in 24 Hours, Second Edition by Jonathan Feldman

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Router Theory

Each router listens on each one of its multiple interfaces for route (also called forwarding) requests.

When a router receives a packet destined for a different network segment, the router must decide to which of its network interfaces it will direct the packet. If the router is connected directly to the destination VLAN, it just plops it out of the interface that’s connected to that VLAN; otherwise, it must hand it off to another router that either is attached to that VLAN or is closer to the directly connected router.

Routing Tables

Obviously, if the router has a direct connection to a particular segment, it knows how to route the packet there. But what if the router you hand the packet to isn’t directly connected to the destination ...

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