Cisco Command Christmas Calendar #11: show ip interface [brief]

Let's look at the show ip interface [brief] command from yesterday's post in more detail. First, the show ip interface brief command displays a summary of the interfaces and their status on the device. This is very useful to see a quick overview of the IP addresses assigned to the interfaces and whether the interfaces are up or down. Example:

R10#show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0         unassigned      YES unset  administratively down down
GigabitEthernet0/1         unassigned      YES unset  up                    up
GigabitEthernet0/1.102   YES NVRAM  up                    up
GigabitEthernet0/1.210    YES NVRAM  up                    up
Loopback0            YES NVRAM  up                    up

Field descriptions:
  • Interface: type of interface
  • IP-Address: IP address assigned to the interace
  • OK?: "Yes" means that the IP address is valid. "No" means that the IP adrdress is not valid.
  • Method: how the interface configuration was applied 
    • RARP or SLARP--Reverse Address Resolution Protocol (RARP) or Serial Line Address Resolution Protocol (SLARP) request.
    • BOOTP--Bootstrap protocol.
    • TFTP--Configuration file obtained from the TFTP server.
    • manual--Manually changed by the command-line interface.
    • NVRAM--Configuration file in NVRAM.
    • IPCP--ip address negotiated command.
    • DHCP--ip address dhcp command.
    • unset--Unset.
    • other--Unknown.
  • Status: shows the status of the interface
    • up--Interface is up.
    • down--Interface is down.
    • administratively down--Interface is administratively down.
  • Protocol: shows the operational status of the routing protocol on the interface.

One useful piece of information the show ip interface brief command doesn't show is the subnet mask. However, this can be seen with the more verbose show ip interface command. If a particular interface is not specified in the command, the full usability status for all interfaces configured for IP is displayed. Example:

R10#show ip interface
GigabitEthernet0/0 is administratively down, line protocol is down
  Internet protocol processing disabled
GigabitEthernet0/1 is up, line protocol is up
  Internet protocol processing disabled
GigabitEthernet0/1.102 is up, line protocol is up
  Internet address is
  Broadcast address is
  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 fast switching on the same interface 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
  Policy routing is disabled
  Network address translation 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

That is a lot of output. The most significant fields are:
  • Internet Address: shows the IP addresss and subnet mask
  • MTU is: MTU value set on the interface, in bytes
  • Outgoing/Incoming access list: shows whether the interface has an outgoing/incoming access list set
  • Split Horizon: shows whether split horizon is enabled
  • IP CEF Switching: shows whether Cisco Express Forwarding is enabled for the interface

Cisco documentation: show ip interface