When configuring a router or switch, we may encounter the terms “line vty 0 4” or “line vty 0 15”. So what does line vty 0 4 and line vty 0 15 mean?

Now we’re going to talk about vTY.


The term VTY is fully called Virtual teletype. A Virtual terminal is used to obtain Telnet or SSH access to a device. A VTY is only used for inbound connections of the device.

The abstract “0-4” indicates that the device can allow up to five virtual connections simultaneously, which can be Telnet or SSH. To some extent, we can say that 5 (0-4) is the connection port of a router or switch. In fact, we may have as many as 16 (0-15) connection ports.

Here is an example where we configure Telnet access to cisco devices and Telnet Settings for passwords

R3(config)#line vty 0 4
R3(config-line)#password Cisco
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Above is cisco’s configuration, let’s take a look at how Huawei devices are configured.

[HUAWEI]user-interface vty 0 4 
[HUAWEI-ui-vty0-4]authentication-mode password
[HUAWEI-ui-vty0-4]set authentication passowrd cipher
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Configuration of H3C:

[H3C]telnet server enable
[H3C]user-interface vty 0 4
[H3C-line-vty0-4]authentication-mode none
[H3C-line-vty0-4]user-role level-3
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In general, vTY configuration is very basic, I hope you can see it, do it, in daily work will not only configuration, but also know what vTY is in the end.