Global ConfigDomain 5.0

line vty [start] [end]

Transitions the CLI into Line Configuration submode for the Virtual Teletype (VTY) interfaces. These are the purely software-based connection ports that allow administrators to access the router remotely via SSH or Telnet.

CLI Deployment Scenarios

Scenario 1: Accessing the Default Block

By default, Cisco devices support 5 concurrent virtual connections, numbered 0 through 4.

Router(config)# line vty 0 4

Router(config-line)#

! Any commands typed here apply equally to all 5 potential remote sessions.

CCNA Exam Gotchas

[!]

Modern Expansion

While legacy hardware only had lines 0 to 4, modern Cisco switches support 16 concurrent sessions (0 to 15). If you only configure line vty 0 4, an attacker could attempt to initiate a 6th simultaneous Telnet session, land on line vty 5, and bypass your security block. Best practice is to configure line vty 0 15 on modern switches.