show ip interface brief is a Cisco IOS command that quickly verifies a router’s interfaces, IPv4 addresses, physical status, and Layer 2 protocol status. Run it from user EXEC or privileged EXEC mode before or after configuration. section 7.3.2 section 7.4
Read the output by checking each column:
- Interface identifies the router interface, such as GigabitEthernet0/0. section 7.3.2
- IP-Address shows the configured IPv4 address or unassigned when none exists. section 7.3.2
- Status reports physical state: up, down, or administratively down when manually disabled. section 7.3.2
- Protocol reports whether the interface’s Layer 2 protocol is functioning; Ethernet interfaces normally show up/up when operational. section 7.3.2
Verify configured interfaces
After assigning 192.168.1.1 to G0/0 and 192.168.2.1 to G0/1 and enabling both interfaces with no shutdown, the command shows both interfaces as manual, up, up. Unassigned interfaces remain administratively down/down until configured and enabled. section 7.3.2 section 7.4
R1# show ip interface brief #1 Interface IP-Address OK? Method Status Protocol GigabitEthernet0/0 unassigned YES unset administratively down down #2 GigabitEthernet0/1 unassigned YES unset administratively down down #2 GigabitEthernet0/2 unassigned YES unset administratively down down #2 GigabitEthernet0/3 unassigned YES unset administratively down down #2 #1 Views information about R1’s interfaces #2 R1’s four interfaces are listed.
Use the annotated R1 listing to match each output column with the router’s four interfaces. section 7.3.2
