The most useful Cisco OS commands

X – port number

How to check configuration for specific port

sh run int f0/X  or show running-config interface fastEthernet 0/X

How to check all configuration 

show running-config

How to change description on port


configure terminal

interfaces  fastEthernet 0/X


How to set up Trunk( Allow few VLAN’s to access one port)

configure terminal
interface FastEthernet0/X
description MY_NAME

switchport trunk encapsulation dot1q
switchport mode trunk
switchport trunk allowed vlan MY_VLAN1,MY_VLAN2


How to setup a Native trunk and what is

Windows is not tagging Vlan so you would need to sometimes setup Native VLAN tagging so all the packets which are not tagged will be given this VLAN tag

configure terminal
interface FastEthernet0/X

switchport trunk native My-VLAN

How to save running configuration


copy running-config startup-config

List of Basic Most Used Network Ports

Most Common Ports:

20 & 21: File Transfer Protocol (FTP)
22: Secure Shell (SSH)
23: Telnet remote login service
25: Simple Mail Transfer Protocol (SMTP)
53: Domain Name System (DNS) service
80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web110: Post Office Protocol (POP3)
119: Network News Transfer Protocol (NNTP)
143: Internet Message Access Protocol (IMAP)
161: Simple Network Management Protocol (SNMP)
194: Internet Relay Chat (IRC)
443: HTTP Secure (HTTPS)
465: SMTP Secure (SMTPS)

1433: Windows SQL Server