I am reading through documentation which talks about "Serial network interface" something which also shows up when IOS boots.
I never see "Serial network interface" defined anywhere. If my router says 2 Serial network interface(s) what does that mean? Does it mean that those 2 Serial network interfaces can support Ethernet? What about frame relay?
While not a duplicate, you should read my answer here: Why do modern routers not require clock settings anymore?
The short answer is that before Ethernet, built-in T1 interfaces, WIC cards, etc., routers connected to each other with serial ports. Usually that serial port connected the router to something like a T1 CSU/DSU or an ISDN adapter. But the port on the router was a serial port.
I am not aware of a solution to convert a serial port on a Cisco router to Ethernet. But serial ports do support most other communications protocols like T-carriers, x.25, frame relay, etc.
SNI is the term telephone company employees use to refer to the aluminium boxes commonly attached to the side of your home. It usually is a single pair of copper telephone cables that can be rewired to accommodate two or more common extension lines within the home. Its a telephone splitter...
