show ip interface brief – Fast Interface Overview & Troubleshooting

Purpose of `show ip interface brief` Command

Definition: show ip interface brief is a Cisco IOS command providing a concise summary of all Layer 3 interfaces on a router or switch.

Quickly displays interface names, IP assignments, and operational status.
Essential for rapid verification and troubleshooting.
Prepares the engineer for more advanced diagnostics if needed.

Common Usage Scenarios

Verify which interfaces are up or down.
Check IP assignments at a glance.
Spot configuration or connectivity problems quickly.
Prepare for in-depth troubleshooting (e.g., check details, errors, configs).

Understanding Output Fields

Field	Description
Interface	Name (e.g., GigabitEthernet0/1, FastEthernet0/0)
IP-Address	IPv4 address assigned (or "unassigned")
OK?	Hardware status (usually "YES" if operational)
Method	How IP was assigned: manual, DHCP, unset
Status	Physical (Layer 1) status: up, down, administratively down
Protocol	Layer 2/3 protocol status: up (running), down (not running)

Sample Output Example

Router# show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0     192.168.1.1     YES manual up                    up
GigabitEthernet0/1     unassigned      YES unset  administratively down down
Serial0/0/0            10.0.0.1        YES manual up                    up
Loopback0              172.16.1.1      YES manual up                    up

Interpreting Interface Statuses

Status	Protocol	Meaning
up	up	Interface fully operational
up	down	Layer 1 (physical) is fine, but Layer 2/3 not working
administratively down	down	Disabled via config; use `no shutdown` to enable
down	down	Cable unplugged, hardware failure, or remote end down

Status: "up" (Layer 1 is good), "down" (physical problem), "administratively down" (shut down by config)
Protocol: "up" (protocols running), "down" (not running)

Using the Command for Troubleshooting

Find interfaces that are down or disabled (easy to spot errors).
Spot missing or misconfigured IPs (shows as "unassigned").
Mismatch (up/down) may indicate Layer 2 issues (cabling, speed/duplex, neighbor down).
See if interfaces are up but not configured with an IP address.

Example: Interface shutdown (needs enabling)

GigabitEthernet0/2     unassigned     YES unset  administratively down down

Action: Run no shutdown in interface config mode.

Example: Physical issue

GigabitEthernet0/3     192.168.20.1   YES manual down   down

Action: Check cable, SFP, or remote end.

Example: All interfaces up

GigabitEthernet0/0     192.168.10.1   YES manual up     up
GigabitEthernet0/1     10.10.10.2     YES manual up     up

Variations and Related Commands

show interfaces: Detailed info (errors, speed, packets, etc.)
show interfaces status (switches): Layer 2 port/VLAN status
show ip interface: More detailed Layer 3 info (ACLs, helpers)
show running-config interface [name]: Full config for a specific interface

Tip: Use filtering for quick searches, e.g.:
show ip interface brief | include down

Use in Different Cisco Devices

Routers & Layer 3 Switches: Shows routed interfaces.
Layer 2 Switches: Only SVI (VLAN) interfaces and routed ports appear.
Output formatting may differ slightly by model or IOS version.

Filtering and Sorting Output

To filter for a specific interface:
show ip interface brief | include GigabitEthernet0/1
To show all interfaces that are down:
show ip interface brief | include down

Exam Tips and Key Points

show ip interface brief is a primary troubleshooting command on Cisco devices.
Know what each column means and typical status/protocol combinations.
"administratively down" means the interface is shut down by config—not a physical problem.
Always use this command before deeper diagnostics.
Combine with show run interface [name] for complete troubleshooting.

Show IP Interface Brief Command Quiz

1. What is the primary purpose of the `show ip interface brief` command?

A. Display a concise summary of all Layer 3 interfaces and their status B. Show detailed packet statistics for interfaces C. List all VLANs on the switch D. Configure IP addresses on interfaces

Correct answer is A. This command gives a quick overview of interface names, IPs, and operational status.

2. In the `show ip interface brief` output, what does the "Method" column indicate?

A. Interface duplex setting B. How the IP address was assigned (manual, DHCP, etc.) C. Hardware status of the interface D. Layer 2 VLAN assignment

Correct answer is B. The Method column shows if the IP was set manually, by DHCP, or unset.

3. What does the status "administratively down" mean in the `show ip interface brief` output?

A. Physical cable is unplugged B. Interface is up but protocol is down C. Interface has been disabled via configuration (shutdown command) D. Interface is up and functioning normally

Correct answer is C. "Administratively down" means the interface was manually shut down via config.

4. Which columns in the `show ip interface brief` output indicate if the interface is operational?

A. Method and Protocol B. Interface and IP-Address C. IP-Address and Status D. Status and Protocol

Correct answer is D. "Status" shows physical line state and "Protocol" shows Layer 2/3 operation.

5. If an interface shows `Status: up` but `Protocol: down`, what does it likely mean?

A. Physical layer is fine, but Layer 2/3 protocol is not working B. The interface is administratively down C. The interface is disabled in configuration D. Interface is operating normally

Correct answer is A. This means the cable/link is connected but protocol issues exist.

6. What information is NOT typically shown by `show ip interface brief`?

A. Interface IP address B. Packet error counts C. Interface name D. Interface status

Correct answer is B. Packet error statistics are shown in detailed show interfaces output, not in brief summary.

7. Which command can be used to filter the output of `show ip interface brief` for a specific interface?

A. show interfaces status [interface] B. show running-config interface [interface] C. show ip interface brief | include [interface] D. show ip interface [interface]

Correct answer is C. The pipe operator and "include" filter output lines matching the interface name.

8. What would the output look like for an interface that is administratively down?

A. Status: up, Protocol: up B. Status: down, Protocol: up C. Status: down, Protocol: down D. Status: administratively down, Protocol: down

Correct answer is D. Interfaces shut down in configuration show "administratively down" status.

9. What does the "OK?" column indicate in the `show ip interface brief` output?

A. If the IP address is reachable B. Hardware status of the interface C. Whether the interface is administratively down D. Whether the IP address was assigned by DHCP

Correct answer is B. The "OK?" column usually shows "YES" if the hardware is working properly.

10. Which of these commands provides more detailed interface information than `show ip interface brief`?

A. show interfaces B. show ip route C. show running-config D. show vlans

Correct answer is A. The "show interfaces" command provides detailed stats like errors and bandwidth.

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show ip interface brief – Fast Interface Overview & Troubleshooting

Purpose of show ip interface brief Command