Contents

• Configuring Telnet
• Information About the Telnet Server
• Prerequisites for Telnet
• Guidelines and Limitations for Telnet
• Default Setting for Telnet
• Configuring Telnet
• Enabling the Telnet Server
• Starting an IP Telnet Session to a Remote Device
• Clearing Telnet Sessions
• Verifying the Telnet Configuration
• Feature History for Telnet

Configuring Telnet

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This chapter contains the following sections:

• Information About the Telnet Server
• Prerequisites for Telnet
• Guidelines and Limitations for Telnet
• Default Setting for Telnet
• Configuring Telnet
• Verifying the Telnet Configuration
• Feature History for Telnet

Information About the Telnet Server

The Telnet protocol enables you to set up TCP/IP connections to a host. Telnet allows a user at one site to establish a TCP connection to a login server at another site and then pass the keystrokes from one device to the other. Telnet can accept either an IP address or a domain name as the remote device address.

Prerequisites for Telnet

You have configured IP on a Layer 3 interface, out of band on the mgmt 0 interface.

Guidelines and Limitations for Telnet

• The Telnet server is disabled by default.
• Cisco NX-OS commands may differ from Cisco IOS commands.

Default Setting for Telnet

Parameter	Default
Telnet server	Disabled

Configuring Telnet

Enabling the Telnet Server

The Telnet server is enabled by default, but you can reenable the server if necessary.

Before You Begin

Log in to the CLI in EXEC mode.

Procedure

	Command or Action	Purpose
Step 1	switch# configure terminal	Enters global configuration mode.
Step 2	switch(config)# feature telnet	Enables the Telnet server.
Step 3	switch(config)# show telnet server	(Optional) Displays the Telnet server configuration.
Step 4	switch(config)# copy running-config startup-config	(Optional) Copies the running configuration to the startup configuration.

The following example enables the Telnet server:

switch# configure terminal
switch(config)# feature telnet
switch(config)# show telnet server
telnet service enabled
switch(config)# copy running-config startup-config

Starting an IP Telnet Session to a Remote Device

Before You Begin

• Log in to the CLI in EXEC mode.
• Verify that the Telnet server is enabled and that the server is also enabled on the remote device.
• Obtain the hostname for the remote device and, if needed, the username on the remote device.

Procedure

	Command or Action	Purpose
Step 1	switch# telnet {ip address | host-name} [port-number] [vrf vrf-name]	Creates an IP Telnet session to the specified destination. The keywords and arguments are as follows: port-number—Port number to use for this session. The range is from 1 to 65535. The default port number is 23. vrf-name—Default virtual routing and forwarding (VRF) instance.

Clearing Telnet Sessions

Before You Begin

Log in to the CLI in EXEC mode.

Procedure

	Command or Action	Purpose
Step 1	switch# show users	Displays user session information.
Step 2	switch# clear line vty-line	Clears a user Telnet session. vty-line—The Virtual Teminal Line (VTY) to clear.
Step 3	switch# show users	(Optional) Displays user session information.

The following example clears a Telnet session:

switch# show users
NAME     LINE         TIME         IDLE          PID COMMENT
admin    tty1         Jul 25 19:13  old         2867
admin    pts/1        Jul 28 14:04   .         31453 (::ffff:171.70.209.8)
admin    pts/2        Jul 28 14:04   .         31475 (171.70.209.8)*
switch# clear line 1
switch# show users
NAME     LINE         TIME         IDLE          PID COMMENT
admin    tty1         Jul 25 19:13  old         2867
admin    pts/2        Jul 28 14:04   .         31475 (171.70.209.8)*
switch#

Verifying the Telnet Configuration

Use one of the following commands to verify the configuration:

Command	Purpose
show running-config security [all]	Displays the SSH and user account configuration in the running configuration. The all keyword displays the default values for the SSH and user accounts.
show telnet server	Displays the Telnet server configuration.
show hosts	Displays the configuration details for current hosts.

Example 1: show running-config security all

The following example displays the user account configuration in the running configuration for :

switch(config)# show running-config security all

!Command: show running-config security all
!Time: Tue Sep 17 22:04:20 2013

version 5.2(1)SK1(2.1)
feature telnet
feature http-server
no feature scp-server
no feature sftp-server
feature ssh

username adminbackup password 5 ! role network-operator
username admin password 5 $1$qnBf/DZs$SADurdd7yy/VMA19E./N11 role network-admin
username admin keypair rsa
username ajidas password 5 $1$L8yMjMMy$xIGNCA.CkgnVY70nBqnhr1 expire 2020-12-30 
role network-operator
password strength-check

banner motd #Nexus 1000v Switch
#

ssh key rsa 2048 
no ssh key dsa

Example 2: show telnet server

The following example displays the Telnet server configuration:

switch(config)# show telnet server
telnet service enabled

Example 3: show hosts

The following example displays the configuration details for current hosts:

switch(config)# show hosts
DNS lookup enabled
Name/address lookup uses domain service
Name servers are 255.255.255.255


Host                    Address
host1                   192.0.2.0
host2                   198.51.100.0
host3                   203.0.113.0

Feature History for Telnet

Feature Name		Feature Information
Telnet	Release 5.2(1)SK1(2.1)	This feature was introduced.