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The first configuration on any new device is a small ceremony: name it, address its interfaces, save it. That sequence hasn't changed in twenty years and probably won't. Here's the canonical version.
Router1# configure terminalRouter1(config)# hostname R1-HQR1-HQ(config)# ip domain-name corp.example.comR1-HQ(config)# exitR1-HQ# write memoryBuilding configuration...[OK]
The hostname shows up in the CLI prompt, in syslog messages, in SNMP identification, and in SSH prompts. It's not cosmetic — it's how you and your tools distinguish one device from another. Domain-name matters for SSH key generation and DNS resolution.
R1-HQ(config)# interface gigabitEthernet0/0R1-HQ(config-if)# description Uplink-to-ISPR1-HQ(config-if)# ip address 203.0.113.10 255.255.255.252R1-HQ(config-if)# no shutdownR1-HQ(config-if)# exitR1-HQ(config)# interface gigabitEthernet0/1R1-HQ(config-if)# description LAN-UsersR1-HQ(config-if)# ip address 10.10.20.1 255.255.255.0R1-HQ(config-if)# no shutdownR1-HQ(config-if)# endR1-HQ# write memory
Three things on every interface: a description (for humans), an IP and mask (if it's a Layer 3 port), and `no shutdown` (to bring it up — interfaces are administratively down by default on routers). Forgetting the `no shutdown` is the single most common beginner mistake.
Interfaces on Cisco routers are administratively down by default. Interfaces on switches are NOT — they come up as soon as a cable is plugged and the VLAN exists. This difference trips people up constantly.
Both configured interfaces show `up/up`. The `OK? YES NVRAM` tells you the address came from the saved config. The unconfigured interfaces show `administratively down` — they're shut.
| Status | Protocol | Meaning |
|---|---|---|
| up | up | Everything works — Layer 1 and Layer 2 both healthy |
| up | down | Physical link up, but Layer 2 issue (VLAN missing, no keepalives) |
| down | down | Physical link down — cable, far end, or shutdown |
| administratively down | down | You shut it — `no shutdown` needed |
Configuration changes are live immediately in running-config but lost on reboot unless you save. `write memory` (or `copy running-config startup-config`) is muscle memory you must build. The only exception: during initial setup before a save, changes are ephemeral — great for testing, dangerous if you forget what's persistent.
Basic config in hand. Next lesson: securing the device with passwords, banners, and access controls.
Finish the lesson once you have worked through the material. This awards ★ 30 XP.