Essential CCNA Commands
The Cisco IOS commands that show up again and again on the CCNA — grouped by what you're actually doing, with the show commands that save you in troubleshooting questions.
Moving between modes
Router> enable ! user EXEC -> privileged EXEC
Router# configure terminal ! -> global config (short: conf t)
Router(config)# interface g0/0 ! -> interface config
Router(config-if)# exit ! back up one level
Router(config-if)# end ! jump straight to privileged EXEC (or Ctrl+Z)Basic device setup
Router(config)# hostname R1
R1(config)# enable secret Cisco123 ! encrypted privileged password
R1(config)# service password-encryption ! obscure plaintext passwords
R1(config)# banner motd # Authorized access only #
R1# show running-config ! the live config (short: show run)
R1# copy running-config startup-config ! save it (or: write memory)
R1# show version ! IOS version, uptime, modelInterfaces
R1(config)# interface g0/0
R1(config-if)# description Link to SW1
R1(config-if)# ip address 192.168.1.1 255.255.255.0
R1(config-if)# no shutdown ! bring the interface up
R1# show ip interface brief ! quick up/down + IP table (show ip int br)
R1# show interfaces status ! switch port status/VLAN/speed"Administratively down" means someone needs to type no shutdown. "Down/down" usually means a cabling or far-end problem.
VLANs and switchports
SW1(config)# vlan 10
SW1(config-vlan)# name SALES
SW1(config)# interface g0/1
SW1(config-if)# switchport mode access
SW1(config-if)# switchport access vlan 10
SW1(config)# interface g0/24
SW1(config-if)# switchport mode trunk
SW1# show vlan brief ! which ports are in which VLAN
SW1# show interfaces trunk ! trunk links and allowed VLANsRouting
! Static route
R1(config)# ip route 10.2.2.0 255.255.255.0 192.168.1.2
! Default route
R1(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.2
! OSPF
R1(config)# router ospf 1
R1(config-router)# network 192.168.1.0 0.0.0.255 area 0
R1# show ip route ! the routing table
R1# show ip ospf neighbor ! OSPF adjacencies (Full = good)
R1# show ip protocols ! which routing protocols are runningSSH and remote access
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa ! choose 1024+ modulus
R1(config)# username admin secret StrongPass
R1(config)# line vty 0 4
R1(config-line)# transport input ssh
R1(config-line)# login local
R1# show sshThe troubleshooting show commands
A huge share of exam questions are "here's the output — what's wrong?" Know what each of these tells you:
| Command | Tells you |
|---|---|
| show ip interface brief | Which interfaces are up and their IPs |
| show ip route | How the router reaches each network |
| show vlan brief | Port-to-VLAN assignments |
| show mac address-table | Which MAC is on which switch port |
| show cdp neighbors | Directly connected Cisco devices |
| show ip ospf neighbor | OSPF adjacency state |
| ping / traceroute | Reachability and the path taken |
Don't just read commands — type them
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