Cisco IOS Device and Interface Configuration

Start with Cisco IOS Access Modes and Essential Commands so that configuration mode and save operations are familiar.

Basic identity and passwords

enable
configure terminal
hostname R1
no ip domain-lookup
enable secret <strong-enable-secret>
service password-encryption
end

service password-encryption is not a substitute for strong authentication; it provides only weak reversible obfuscation for some stored passwords. Use a secret placeholder in notes and set the real value interactively.

Console and VTY access

configure terminal
line console 0
 logging synchronous
 exec-timeout 10 0
 login local
exit
username admin privilege 15 secret <strong-admin-secret>
line vty 0 4
 login local
 transport input ssh
exit
end

The SSH prerequisites are covered in the next article. Do not enable Telnet on a production or shared network.

Configure an interface

configure terminal
interface gigabitEthernet 0/1
 description Uplink to lab switch
 ip address 192.0.2.1 255.255.255.0
 no shutdown
end

The address and mask must match the intended subnet. See IPv4 Subnets, Netmasks, and CIDR for the calculation, then verify:

show ip interface brief
show interfaces gigabitEthernet 0/1

An interface can be administratively up but operationally down because of cabling, speed, peer configuration, or a disabled remote port.

Save after testing

copy running-config startup-config