While going through any Cisco Router or Switch configuration, we may come across the term of “line vty 0 4” or “line vty 0 15“.
Let’s discuss these keywords in more detail and their requirement in the configuration of the Cisco Router or Switches –
The term “vty” stands for Virtual teletype. VTY is a virtual port and used to get Telnet or SSH access to the device.VTY is solely used for inbound connections to the device. These connections are all virtual with no hardware associated with them.
The abstract “0 – 4” means that the device can allow 5 simultaneous virtual connections which may be Telnet or SSH. In a way, we may say that 5 (0 – 4) are connection ports to the Router or Switch. In fact, we may have connection ports up to 16 (0 – 15).
Here is an example where we configure telnet access to a cisco device and password for telnet facility –