运维少年系列 python and cisco （1）
本系列文章需要各位具有CCNA/HCNA基础知识（知道命令怎么敲）
本系列文章需要使用到的python版本为2.7，模块为paramiko。
为何使用python2.7而不是3.x？因为绝大部分系统都自带了2.7，就这么简单~
paramiko模块功能十分强大，最常使用的就是其SSH登录的功能，使用paramiko实现了SSH登录之后，还可以执行命令，实现远程配置设备。在代码编写部分我会向各位简单的介绍一下每段代码的作用。
系列文章不会很多（预计2-3篇？），毕竟就一个模块，从简单到稍微复杂一点，然后从单点到批量，然后到异常处理，大概的路线就是这样。文章有些地方可能描述的不准确，请大家多多指教。
1) 拓扑图
使用GNS3做一个简单的拓扑，将centos桥接GNS3中，使路由器与centos相连。
2) 交换机配置
交换机配置ssh，注意密钥的长度不要使用512，不然登录会失败。
R3(config)#hostname R3
R3(config)#ip domain name yunwsn.com
R3(config)#crypto key generate rsa
The name for the keys will be: R3.yunwsn.com
Choose the size of the key modulus in the range of 360 to 2048 for your
General Purpose Keys. Choosing a key modulus greater than 512 may take
a few minutes.
How many bits in the modulus [512]: 2048
% Generating 512 bit RSA keys, keys will be non-exportable...[OK]
*Mar 1 00:11:52.127: %SSH-5-ENABLED: SSH 2.0 has been enabled
R3(config)#
R2(config)#line vty 0 10
R2(config-line)#transport input ssh
R2(config-line)#login local
R2(config-line)#exit
R1(config)#username yunwsn privilege 15 password 123456
R1(config)#enable password 123456
3) python配置
安装paramiko
没有pip的百度安装一下吧~
[root@yunwei ~]# pip install paramiko
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7.
Collecting paramiko
Using cached https://files.pythonhosted.org/packages/cf/ae/94e70d49044ccc234bfdba20114fa947d7ba6eb68a2e452d89b920e62227/paramiko-2.4.2-py2.py3-none-any.whl
Requirement already satisfied: cryptography>=1.5 in /usr/lib64/python2.7/site-packages (from paramiko) (2.6.1)
Requirement already satisfied: pynacl>=1.0.1 in /usr/lib64/python2.7/site-packages (from paramiko) (1.3.0)
Requirement already satisfied: pyasn1>=0.1.7 in /usr/lib/python2.7/site-packages (from paramiko) (0.4.5)
Requirement already satisfied: bcrypt>=3.1.3 in /usr/lib64/python2.7/site-packages (from paramiko) (3.1.6)
Requirement already satisfied: enum34; python_version < "3" in /usr/lib/python2.7/site-packages (from cryptography>=1.5->paramiko) (1.1.6)
Requirement already satisfied: asn1crypto>=0.21.0 in /usr/lib/python2.7/site-packages (from cryptography>=1.5->paramiko) (0.24.0)
Requirement already satisfied: cffi!=1.11.3,>=1.8 in /usr/lib64/python2.7/site-packages (from cryptography>=1.5->paramiko) (1.12.3)
Requirement already satisfied: six>=1.4.1 in /usr/lib/python2.7/site-packages (from cryptography>=1.5->paramiko) (1.12.0)
Requirement already satisfied: ipaddress; python_version < "3" in /usr/lib/python2.7/site-packages (from cryptography>=1.5->paramiko) (1.0.22)
Requirement already satisfied: pycparser in /usr/lib/python2.7/site-packages (from cffi!=1.11.3,>=1.8->cryptography>=1.5->paramiko) (2.19)
Installing collected packages: paramiko
Successfully installed paramiko-2.4.2
[root@yunwei ~]#
代码编写
#!/usr/bin/env python
import paramiko # 导入paramiko模块
import time # 导入time模块，这个后面会用到
host = '192.168.108.254' # 定义主机IP
user = 'yunwsn' # 定义登录的用户名
passwd = '123456' # 定义使用的密码
s = paramiko.SSHClient() # 实例化，啥意思?请看注释①
s.set_missing_host_key_policy(paramiko.AutoAddPolicy()) # 请看注释②
s.connect(host,username=user,password=passwd,look_for_keys=False,allow_agent=False) # 定义登录的IP、用户名和密码
print 'login success.' # 登录成功提示
cmd = s.invoke_shell() # 创建一个交互式的shell，实现多发送条命令
cmd.send("conf t \n") # 发送命令
time.sleep(1) # 睡眠1s，特别重要，注释③
cmd.send("int f0/1 \n")
time.sleep(1)
cmd.send("ip add 1.1.1.2 255.255.255.0 \n")
time.sleep(1)
cmd.send("end \n")
time.sleep(1)
cmd.send("show ip int bri\n ")
time.sleep(1)
output = cmd.recv(65535) # 接收输出
print output # 打印输出
cmd.close() # 关闭交互式shell
注释：
①：实例化可以简单的理解为，将paramiko.SSHClient类的所有属性赋予s。就比如，张三的父亲是富一代，那么属性就是有钱，然后…嗯，差不多，实例化之后，s可以使用原先paramiko.SSHClient()下面所有的办法，其实也可以将其理解为一个别名，给paramiko.SSHClient取个别名叫s
②：在登陆时，有些设备会提示以下内容，需要用户输入【yes】才能进行下一步，而使用了这个参数，则不需要输入yes
[root@yunwei cisco]# ssh [email protected]
The authenticity of host '192.168.108.254 (192.168.108.254)' can't be established.
RSA key fingerprint is SHA256:FBFOoRUMkKYCyDbpZKkRiuhCbiYuOX8EuHLUMoN0C/M.
RSA key fingerprint is MD5:b9:ad:29:24:43:bb:48:8c:58:3e:ce:03:a4:74:e2:cf.
Are you sure you want to continue connecting (yes/no)?
③：在我的GNS3中，路由器反应比较慢，比如我输入了conf t ，他可能过了0.5s才能进入config模式，python的下一条命令int f0/1可能在0.5s的时候就执行了，导致命令执行不成功，所以，我在中间加入了一个睡眠，1s后再执行下个命令，大家在使用的时候可以修改这个时间，使命令执行时间更加合理。
4) 实现效果
[root@yunwei cisco]# python ywsn_p_c_lab1.py
login success.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int f0/1
R1(config-if)#ip add 1.1.1.2 255.255.255.0
R1(config-if)#end
R1#show ip int bri
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.108.254 YES manual up up
FastEthernet0/1 1.1.1.2 YES manual up down
FastEthernet0/2 unassigned YES unset up down
FastEthernet0/3 unassigned YES unset up down
FastEthernet0/4 unassigned YES unset up down
FastEthernet0/5 unassigned YES unset up down
FastEthernet0/6 unassigned YES unset up down
FastEthernet0/7 unassigned YES unset up down
FastEthernet0/8 unassigned YES unset up down
FastEthernet0/9 unassigned YES unset up down
FastEthernet0/10 unassigned YES unset up down
FastEthernet0/11 unassigned YES unset up down
FastEthernet0/12 unassigned YES unset up down
FastEthernet0/13 unassigned YES unset up down
FastEthernet0/14 unassigned YES unset up down
FastEthernet0/15 unassigned YES unset up down
Vlan1 unassigned YES unset up down
R1#
[root@yunwei cisco]#
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