（ps：第一次写博客，大佬们轻喷，只是单纯分享学习，加强自身记忆）
实验软件为Cisco Packet
拓扑及设备
（笔记本是console线连接，PC为远程）
路由器IP与子网掩码并打开端口
PC0设置
利用telnet传输协议使得PC0能虚拟远程访问路由器F0/0端口：
路由器命令如下：(缺省部分可用Tab键补齐)
Router>en
Router#conf t
Router(config)#line vty 0 4
Router(config-line)#login local
Router(config-line)#transport input telnet
Router(config)#username 2333 password 2333 前面的2333为用户名，后者为密码进入PC0，进入下图所示的comman prompt
敲入如下命令：
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>
此时，已成功通过telnet协议实现PC0远程登录。
在路由器中敲入以下命令可以限制设置账户的密码长度（此处是10，可任意更改）
Router(config)#security passwords min-length 10
给console线路设置密码
此时需要进入笔记本的终端中进行设置（如下图红线处所示）
进入终端，输入如下命令：
Router>en
Router#conf t
Router(config)#line cons 0
Router(config-line)#password cisco
% Password too short - must be at least 10 characters. Password not configured.
Router(config-line)#password cisco123456
Router(config-line)#login看中间我设置的密码保护就生效了。
这样一直退出后，再进入全局模式下得输入密码了。
之后用PC0登录路由器时出现了以下问题：
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>
Router>en
% No password set.
Router>enable
% No password set.出现了No password set的情况，后面发现路由器没有设置enable密码，自然登录的用户就莫得权限了。
Router(config)#enable password 1234567890在路由器设置完enable密码时，再用PC0登录
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...
% Connection refused by remote host
PC>
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>
Router>en
Password:
Router#
Router#成功进入了呢
Router(config)#service password-encryption 这段命令可以在show running-encryption下把密码换成思科自有的加密
阻塞登录的block-for命令
Router(config)#login block-for 120 attempts 5 within 60含义为如果在60秒内登录失败，登录将会被禁止120秒
测试效果：
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>
Router>en
% No password set.
Router>enable
% No password set.
Router>cisco123456
Translating "cisco123456"...domain server (255.255.255.255)
% Unknown command or computer name, or unable to find computer address
Router>enable
% No password set.
Router>en
% No password set.
Router>
Router>en
% No password set.
Router>ex
[Connection to 192.168.100.100 closed by foreign host]
PC>
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>en
% No password set.
Router>
[Connection to 192.168.100.100 closed by foreign host]
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
Router>en
% No password set.
Router>
Router>
Router>
Router>enable
% No password set.
Router>ex
[Connection to 192.168.100.100 closed by foreign host]
PC>
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
% Login invalid
Username:2333
Password:
% Login invalid
Username: 2333
Password:
[Connection to 192.168.100.100 closed by foreign host]
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...Open
User Access Verification
Username: 2333
Password:
% Login invalid
Username: 2333
Password:
[Connection to 192.168.100.100 closed by foreign host]
PC>telnet 192.168.100.100
Trying 192.168.100.100 ...
% Connection refused by remote host连续输入错误的密码后，被禁止登录了。
ps：排版搞得有点混，系在不好意思了。本人也在初学，出问题再正常不过了，有大佬指正错误我会很感激！谢谢大家观看！