Telnet协议是TCP/IP协议族中的一员，是Internet远程登陆服务的标准协议和主要方式。它为用户提供了在本地计算机上完成远程主机工作的能力。在终端使用者的电脑上使用telnet程序，用它连接到服务器。终端使用者可以在telnet程序中输入命令，这些命令会在服务器上运行，就像直接在服务器的控制台上输入一样。可以在本地就能控制服务器。要开始一个telnet会话，必须输入用户名和密码来登录服务器。Telnet是常用的远程控制Web服务器的方法。
环境
- Cisco Packet Tracer 5.3
- Windows 10
操作
操作：按照如图所示连接拓扑图
（1）配置PC IP
PC0 设置
192.168.1.2/24
PC1 设置
192.168.1.3/24
（2）配置交换机VLAN1 IP
/* part1 为vlan配置ip并开启vlan */
Switch>enable
Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface vlan 1
Switch(config-if)#ip address 192.168.1.1 255.255.255.0
Switch(config-if)#no shutdown
%LINK-5-CHANGED: Interface Vlan1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up
Switch(config-if)#
/ Part2 查看已配置的IP /
Switch(config-if)#^Z
Switch#
%SYS-5-CONFIG_I: Configured from console by console
Switch#show running-config
…
interface Vlan1
ip address 192.168.1.1 255.255.255.0
/ Part3 开启Vlan /
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface vlan 1
Switch(config-if)#no shutdown
/ Part4 查看Vlan状态 /
Switch(config-if)#^Z
Switch#
%SYS-5-CONFIG_I: Configured from console by console
Switch#show interfaces vlan 1
Vlan1 is up, line protocol is up
…
**（3）配置交换机本地登录口令**
/ Part 1 设置明文密码/
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#enable password 123
// 注：取消密码可用no enable password
/ Part 2查看设置的密码 /
Switch(config)#^Z
Switch#
%SYS-5-CONFIG_I: Configured from console by console
Switch#show running-config
…
enable password 123
…
**（4）配置交换机远程登陆及验证**
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#line vty 0
Switch(config-line)#password 123 //（Telnet密码为123）
Switch(config-line)#login local //（login是开启远程登录密码验证，login local不但要求TELNET密码，还要求提供用户名）
Switch(config-line)#
**（5）添加可远程登陆交换机的用户**
/ Part 1 添加用户 /
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#line vty 0
Switch(config-line)#password 123
Switch(config-line)#login local
Switch(config-line)#
Switch(config-line)#exit
Switch(config)#username admin password admin
/ Part 2 查看添加的用户 /
Switch(config)#exit
Switch#
%SYS-5-CONFIG_I: Configured from console by console
Switch#show running-config
…
username admin password 0 admin
…
<br />**（6）测试连接**
// 在PC0的CMD中测试
/ Part 1 Ping交换机 /
PC>ping 192.168.1.1
Pinging 192.168.1.1 with 32 bytes of data:
Reply from 192.168.1.1: bytes=32 time=5ms TTL=255
Reply from 192.168.1.1: bytes=32 time=5ms TTL=255
Reply from 192.168.1.1: bytes=32 time=6ms TTL=255
Reply from 192.168.1.1: bytes=32 time=6ms TTL=255
Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 5ms, Maximum = 6ms, Average = 5ms
/ Part 2 Telnet 连接交换机 /
PC>telnet 192.168.1.1
Trying 192.168.1.1 …Open
User Access Verification
Username: admin
Password:
Switch>
**（7）配置多用户连接**
// 在PC0连接的前提下，再使用PC1尝试连接
/ Part 1 PC1 Ping Switch /
PC>ping 192.168.1.1
Pinging 192.168.1.1 with 32 bytes of data:
Request timed out.
Reply from 192.168.1.1: bytes=32 time=6ms TTL=255
Reply from 192.168.1.1: bytes=32 time=6ms TTL=255
Reply from 192.168.1.1: bytes=32 time=5ms TTL=255
Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 3, Lost = 1 (25% loss),
Approximate round trip times in milli-seconds:
Minimum = 5ms, Maximum = 6ms, Average = 5ms
/ Part 2 PC1 Telnet 连接Swithc /
PC>telnet 192.168.1.1
Trying 192.168.1.1 …Open
[Connection to 192.168.1.1 closed by foreign host]
// 连接失败，因为交换机vty设置只能同时打开一个会话，下面设置一下，使两台PC可同时访问
/ Part 3 修改Tenlet配置 /
// 可直接在PC0直接进行
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#line vty 0 1
Switch(config-line)#password 123
Switch(config-line)#^Z
/ Part 4 重新尝试Part 2 /
PC>telnet 192.168.1.1
Trying 192.168.1.1 …Open
User Access Verification
Password:
Switch>
// 成功
