What does the show ip interface brief command display?
A one-line-per-interface summary: name, IP address, OK?, Method, Status (Layer 1), and Protocol (Layer 2) — a fast way to see which interfaces are up.
The reason this is one of the most-used IOS commands is that its two rightmost columns, Status and Protocol, separate the physical layer from the data-link layer — and the combination tells you exactly where a dead interface failed. up/up means the interface is fully working. up/down means the cable and signalling are fine (Layer 1 up) but Layer 2 isn't negotiating — often a mismatch like encapsulation or clocking. down/down points at a physical problem: no cable, wrong cable, or the far end is off. And administratively down/down means nobody enabled it — it's still shutdown. Reading those two words saves you from chasing a configuration bug when the real fault is a unplugged cable, which is why technicians run this first.
The show ip interface brief Command:
One of the most frequently used commands, providing a summarized view of all network interfaces on a device.
Output includes:
| Column | Description |
|---|---|
| Interface | Interface name (e.g., GigabitEthernet0/0) |
| IP-Address | IPv4 address assigned (or "unassigned") |
| OK? | Indicates if the IP address is valid |
| Method | How IP was configured (manual, DHCP) |
| Status | Layer 1 status (up/down/administratively down) |
| Protocol | Layer 2 status (up/down) |
Example output:
R1# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 209.165.200.225 YES manual up up
GigabitEthernet0/1 192.168.10.1 YES manual up up
Serial0/1/0 unassigned NO unset down down
Key insight: This is much more concise than show ip interface and provides a quick overview of all interfaces on the device.
Go deeper:
Cisco — Understanding interface status (up/up, up/down, down/down) — what each Status/Protocol combination means and how to chase down the cause.