'''Reverse telnet''' is a specialized application of telnet, where the server side of the connection reads and writes data to a computer terminal line (RS-232 serial port), rather than providing a command shell to the host device. Typically, reverse telnet is implemented on an embedded device (e.g. terminal/console server), which has an Ethernet network interface and serial port(s). Through the use of reverse telnet on such a device, IP-networked users can use telnet to access serially-connected devices.
Reverse telnet can be used to connect to modems or other external asynchronous devices.<ref name="p731">{{cite book |last=Lawson |first=Wayne |url=https://www.google.com/books/edition/Building_Cisco_Remote_Access_Networks/F-S2m40es3cC?hl=en&gbpv=1&dq=%2522reverse+telnet%2522+%2522modem%2522&pg=PA49&printsec=frontcover |title=Building Cisco Remote Access Networks |date=2000-11-15 |publisher=Elsevier |isbn=978-0-08-047614-8 |page= |pages=48–49 |access-date=2025-07-30}}</ref> It is also used to connect to the console port of a router, a switch or other device.<ref name="o821">{{cite book |last=Payne |first=Rob |url=https://www.google.com/books/edition/CCIE_Cisco_Certified_Internetwork_Expert/of76QmGUnAoC?hl=en&gbpv=1&dq=%2522reverse+telnet%2522+console&pg=PA77&printsec=frontcover |title=CCIE: Cisco Certified Internetwork Expert Study Guide: Routing and Switching |last2=Manweiler |first2=Kevin |date=2006-02-20 |publisher=John Wiley & Sons |isbn=978-0-7821-5198-5 |page= |pages=76–78 |access-date=2025-07-30}}</ref>
==Example== On the client, the command line for initiating a "reverse telnet" connection might look like this:
'''telnet 172.16.1.254 2002'''
(The syntax in the above example would be valid for the command-line telnet client packaged with many operating systems, including most Unix operating systems, or available as an option or add-on.)
In this example, 172.16.1.254 is the IP address of the console device, and 2002 is the TCP port associated with a terminal line on the server.
==See also== * Terminal server * Console server
==References== {{Reflist}}
{{DEFAULTSORT:Reverse Telnet}} Category:Internet protocols Category:Internet Protocol based network software Category:Telnet Category:Unix network-related software Category:Out-of-band management