show ip interface
Displays the status and configuration of all IP interfaces on a Cisco router, including IP address, protocol status, and interface statistics, used for verifying interface IP configuration and troubleshooting connectivity issues.
show ip interfaceWhen to Use This Command
- Verify that an interface has the correct IP address and subnet mask after configuration.
- Troubleshoot why an interface is showing 'up' but 'down' at the protocol level.
- Check if an interface is administratively down due to a shutdown command.
- Review interface statistics like input/output errors or broadcast traffic for performance issues.
Command Examples
Basic show ip interface output for a single interface
show ip interface GigabitEthernet0/0GigabitEthernet0/0 is up, line protocol is up Internet address is 192.168.1.1/24 Broadcast address is 255.255.255.255 Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP flow switching is disabled IP CEF switching is enabled IP CEF switching turbo vector IP multicast fast switching is enabled IP multicast distributed fast switching is disabled IP route-cache flags are Fast, CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Probe proxy name replies are disabled Policy routing is disabled Network address translation is disabled WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled BGP Policy Mapping is disabled Input features: MCI Check IPv4 WCCP Redirect outbound is disabled IPv4 WCCP Redirect inbound is disabled IPv4 WCCP Redirect exclude is disabled
Line 1: 'GigabitEthernet0/0 is up, line protocol is up' indicates the interface is operational. 'Internet address is 192.168.1.1/24' shows the configured IP and subnet mask. 'Broadcast address' is the broadcast IP for the subnet. 'MTU' is the maximum transmission unit. 'Helper address' is used for DHCP relay. 'Directed broadcast forwarding' is disabled by default. 'Proxy ARP' is enabled, allowing the router to respond to ARP requests for other hosts. 'Split horizon' is enabled for routing protocols. 'ICMP redirects' and 'unreachables' are sent. 'IP fast switching' and 'CEF switching' are enabled for performance.
Show ip interface brief for a quick overview
show ip interface briefInterface IP-Address OK? Method Status Protocol GigabitEthernet0/0 192.168.1.1 YES NVRAM up up GigabitEthernet0/1 unassigned YES NVRAM administratively down down Serial0/0/0 10.0.0.1 YES manual up up Loopback0 1.1.1.1 YES NVRAM up up
This command provides a summary of all interfaces. 'Interface' is the interface name. 'IP-Address' shows the configured IP or 'unassigned'. 'OK?' indicates if the interface is valid. 'Method' shows how the IP was assigned (NVRAM, manual, DHCP). 'Status' shows line status (up, down, administratively down). 'Protocol' shows line protocol status (up, down). An 'administratively down' status means the interface was manually shut down with the 'shutdown' command.
Understanding the Output
The 'show ip interface' command provides detailed information about IP configuration and status for each interface. The first line shows the interface line status and protocol status: 'up/up' means operational, 'up/down' indicates a layer 1 issue (e.g., cable problem), 'down/down' means the interface is disabled or no cable, and 'administratively down/down' means the interface was manually shut down. The 'Internet address' field shows the IP and subnet mask. 'Broadcast address' is the subnet broadcast. 'MTU' is the maximum packet size. 'Helper address' is used for DHCP relay. 'Directed broadcast forwarding' should be disabled for security. 'Proxy ARP' can be a security concern if enabled. 'Split horizon' is important for routing loops. 'ICMP redirects' and 'unreachables' are sent by default. 'IP fast switching' and 'CEF' indicate hardware acceleration. Look for 'up/up' for operational interfaces; any other status indicates a problem. High error counts (not shown here but available with 'show interfaces') indicate physical issues.
CCNA Exam Tips
CCNA exam tip: Remember that 'show ip interface brief' is the quickest way to see interface status and IP addresses; the 'Status' column shows line status, 'Protocol' shows layer 2 status.
CCNA exam tip: An interface showing 'administratively down' means it was manually disabled with the 'shutdown' command; use 'no shutdown' to enable it.
CCNA exam tip: The 'show ip interface' command shows 'Proxy ARP is enabled' by default; the exam may ask about disabling it for security with 'no ip proxy-arp'.
CCNA exam tip: If the line protocol is 'down' but the interface is 'up', suspect a layer 2 problem (e.g., no keepalives, mismatched encapsulation).
Common Mistakes
Mistake 1: Confusing 'show ip interface brief' with 'show interfaces' — the former shows only IP info, the latter shows all interface details including errors.
Mistake 2: Forgetting that 'show ip interface' without an interface name shows all interfaces; using 'show ip interface brief' is more efficient for a summary.
Mistake 3: Misinterpreting 'administratively down' as a physical problem; it is a configuration issue fixed with 'no shutdown'.
Related Commands
show interfaces
Displays detailed status and statistics for all interfaces or a specific interface, used to verify interface operational state, errors, and performance.
show ip interface brief
Displays a summary of all IP interfaces on the device, including their IP address, status, and protocol state, used for quick verification of interface configuration and connectivity.
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