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 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 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. Infact we may have connection ports upto 16 (0 – 15).
Here is an example where we configure telnet access to a cisco device and password for telnet facility –