- router: any piece of hardware that forwards packets based on their destination IP address
- routers work at the Network Layer of the OSI model and the Internet level of the TCP/IP model
- routers are dedicated boxes that contain at least two connections
- router reads the IP addresses of the packets to determine where to send the packets
- routers examine packets and send the packets to the proper destination
Routing Tables
- router inspects each packet's destination IP address and then sends the IP packet out the correct port
-> each row in a routing table defines a single route
-> each column identifies a specific criteria
-> Destination LAN IP: a defined network ID. Every directly connected network ID is listed here
-> Subnet Mask: needed to define a network ID
- router uses the combination of the destination LAN IP and subnet mask to see if a packet matches the route
-> Gateway: the IP address for the next hop router (where the packet will go next)
-> interface: indicates to the router which port to use
- router compares the destination LAN IP address on each packet toe very listing in the routing table before sending the packet out
- default route tells the router exactly what to do with every incoming packet
- multihomed computers: computers with more than one NIC
- to view routing table type the command: netstat -r
I know time is limited, but I would strongly encourage you to build a small network topology with at least 3 networks (you can put a single machine in each network and a router with 3 ports (NICs) connecting them up) so that you get hands-on experience setting this stuff up. It will really help your understanding of what all these details mean.
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