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.