- Show running-configuration
The show running-config command is used to check the current configuration on router or a switch. The running-configuration is the configuration that is stored in the router’s memory. Changes are made to this configuration file whenever you make changes to the router. But this configuration is not saved until you do a copy running-configuration startup-configuration.
- Copy running-configuration startup-configuration
This command is used to save the running configuration that is currently being modified, to the non-volatile RAM or NVRAM. When the power is down, the NVRAM help preserve this configuration. In other words, if you make changes to the router configuration and don’t apply this command, these changes will be lost after the router reboots. This command can be abbreviated as copy run start.
- show interface
The show interface command is used to display the status of the interface. Among other things, this output provides the interface information such as interface status, protocol status on the interface, utilization, Errors, MTU, etc.
This command is essential for troubleshooting a router or switch interface issues.
- show ip interface & show ip interface brief
The show ip interface command is used to see detailed information about the configuration and status of the IP protocol and its services on the interfaces. The show ip interface brief command provides a brief status of the interfaces on the router, including their IP address, Layer 2 and Layer 3 status.
- config terminal, enable, interface, and router
Cisco routers have different modes to perform specific tasks.
These modes are user configuration mode, privileged mode, global configuration mode, Interface configuration mode or router configuration mode. In user configuration mode, you need to enter username & password (if required) and enable command to enter privileged mode. In privileged mode, you can see everything using show command but cannot make any changes. To make changes you need to enter the global configuration mode by entering configure terminal command. From here, you can make changes to the global parameters. To change a parameter on an interface, you need to enter interface configuration mode with the interface interface type number command. Also, from the global configuration mode, you can go into router configuration by typing router protocol command. To exit from any mode just type exit command.
- Ip address
This is an interface subcommand which is executed in interface configuration mode. It is used to assign an ip address to router’s interface. For example, ip address 192.168.1.1 255.255.255.0 command is used to assign interface with the ip address of 192.168.1.1 and subnet mask 255.255.255.0 or say /24.
- no shutdown/shutdown
By default, router interfaces are in shutdown mode. The no shutdown or no shut command is used to enable an interface or turn it on. This command must be executed in interface configuration mode. When troubleshooting an interface issue, you may need to use a shut and no shut command.
show ip route
The show ip route command is used to see the routing table of the router. This is the list of routes to all networks that the router can reach, their metric and hops. This command can be used in conjunction with OSPF, EIGRP and other routing protocols. To clear the routing table of all routes, you use clear ip route command.
- show version
The show version command is used to see the router’s configuration register, the model of the router, the last time the router was booted, the name of the IOS file, the version of the IOS and the router’s RAM and Flash information.
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