What is the function of line vty in router configuration?

Vty Line Authentication and Authorization

The system supports 20 virtual tty (vty) lines for Telnet, Secure Shell Server (SSH) and FTP services. Each Telnet, SSH, or FTP session requires one vty line. You can add security to your system by

Static and Dynamic Routers

For routing between routers to work efficiently in an internetwork, routers must have knowledge of other network IDs or be configured with a default route. On large internetworks, the routing tables must