Cisco Routers different types of interfaces like Serial, Ethernet, Fast Ethernet, Gigabit Ethernet, Tokenring, FDDI are some of them (A single router may not have all these). The speed of Ethernet, Fast Ethernet and Gigabit Ethernet are different. The speed of Ethernet is 10 Mbps (Megabits per second), Fast Ethernet is 100 Mbps (Megabits per second) and Gigabit Ethernet is 1 Gbps (Gigabits per second)
Most of the latest routers are modular routers. Modular routers are expandable routers by using plug-in components.
The following naming convention is followed for a Cisco Router.
Slot numbers begin with 0 and port numbers begin with 0. Hence the name of the first interface of a WIC2T (modular card with two smart serial interfaces) is serial0/0 and the name of the second port is serial0/1. The short form of the two interface is s0/0 and s0/1.
Old 2500 series routers are not modular, and they had fixed ports. The interface naming convention of these routers is
Hence the name of the first Ethernet interface for non-modular router is ethernet0 or e0, and first Serial interface is serial0 or s0.