corrections made

Author: EthanXHQ

docs/2022计网实验指令参考.md

@@ -235,7 +235,7 @@ PC5>ping 192.168.20.2
 
 ```
 RD(config)#access-list 1 permit 192.168.40.0 0.0.0.255
-RD(config)#ip nat pool exam 192.168.20.4 192.168.20.4 netwask 255.255.255.0
+RD(config)#ip nat pool exam 192.168.20.4 192.168.20.4 netmask 255.255.255.0
 // 注意：Netmask 可能有 netmask A.B.C.D 与 prefix-length N 两种语法，实际操作请输入 `?` 确认
 RD(config)#ip nat inside source list 1 pool exam
 RD(config)#interface g0/0/0