Telnet is a text-based Internet protocol that enables users to manage remote computers from a distance. Commonly used by network administrators, it requires a special login process. When your Cisco router refuses a Telnet connection, it usually means that the configuration is preventing you from getting through. Depending on your network administrator permissions, you may be able to solve the problem on your own; in an office environment, you will need assistance from an administrator.
Some Telnet connections require you to set a password. If your "connection refused" message contains a request to configure a password, you will need to assign an EXEC password to your Cisco router. To do so, you must issue a "show run" command and then set the EXEC password using the command "cbos#set password exec <password>," substituting your choice of password for "<password>." Once you choose a password, run the "show run" command again to check for the "NSOS Root Password" line. Cisco advises that you set an enable password in addition to the EXEC password with the command "cbos#set password enable <password>," substituting your actual password for "<password>," for security purposes.
When you cannot Telnet into your Cisco router from the network (WAN) side, it can indicate a problem with the interface. Cisco recommends that your interface be trained and open to enable WAN connections. Using the "cbos#show int" command, look for the "wan0 Physical Port" line and ensure that the "Mask" column says "Trained." Then, use the "cbos#show int wan0-0" command and look for the line that begins with "RFC1483 State:". If it indicates that the interface is closed, run the command "cbos#set int wan0-0 open."
Virtual Terminal Lines
By default, each Cisco router comes with five virtual terminal lines (VTYs). If all of your VTYs are tied up, your router will refuse the telnet connection. It is possible to add additional VTYs using the "line vty line-number" command. Cisco warns that because VTYs take up a great deal of CPU space, additional lines can cause slower speeds for all users. If you choose to, you can use up to ten VTYs per router.
Cisco routers can be configured with an access list to limit the people who are able to connect through Telnet. If you are trying to connect from a computer with limited access, you will see a "connection refused" message if you are not on the access list or if you do not have the correct password. Unless you are the network administrator, you will not be able to change the passwords; you must contact the administrator to be added to the access list.
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