Line Types and Numbering

© 2004 Cisco Systems, In

Line numbering varies among router platforms. TTY lines correspond to asynchronous interfaces on a one-to-one basis; vty lines are virtual lines that are dynamically assigned to the synchronous interfaces. Usually, vty lines are associated with incoming Telnet sessions.

In the figure shown, m refers to the number of the vty lines. For example, the vty 0 line corresponds to line 10 on a router with eight TTY ports (con = line 0, tty = lines 1 through 8, aux = line 9, vty = lines 10 through 14).

Connections to an individual line are most useful when a dial-out modem, parallel printer, or serial printer is attached to that router line. To connect to an individual line, the remote host or terminal must specify a particular TCP port on the router. If the Telnet protocol is used, that port is 2000 plus the line number. For example:

telnet 131.108.30.40 2001 This command initiates a Telnet connection to line 1 (2000 + 1).

The following line types are used:

■ CON: Console port (available on all Cisco routers)

■ TTY: Asynchronous port.

■ AUX: Auxiliary port (available on most Cisco routers except the Cisco 600, 700, 800, 1000, and 1600 platforms).

■ VTY: Virtual terminal (for incoming Telnet, local-area transport [LAT], or X.25 packet assembler/disassembler [PAD] connections).

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