Routing Table

Principles

1. Every router makes its decision alone, based on the information it has in its own routing table.

2. The fact that one router has certain information in its routing table does not mean that other routers have the same information.

3. Routing information about a path from one network to another does not provide routing information about the reverse, or return, path.

Routers

Cisco IOS will not allow two active interfaces on the same router to belong to the same network.

LAN Interfaces

• Ethernet interface also has a Layer 2 MAC address and participates in the Ethernet LAN in the same way as any other hosts on that LAN. For example, a router Ethernet interface participates in the ARP process for that LAN.
• When two routers are connected directly through the Ethernet interfaces, or when a PC NIC is connected directly to a router Ethernet interface, a crossover cable is used.