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
GigabitEthernet0/1.102 172.19.102.10 YES NVRAM up up
GigabitEthernet0/1.210 202.4.210.10 YES NVRAM up up
Loopback0 192.122.3.10 YES NVRAM up up
Field descriptions:
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 172.19.102.10/25
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 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:
Cisco documentation: show ip interface
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
GigabitEthernet0/1.102 172.19.102.10 YES NVRAM up up
GigabitEthernet0/1.210 202.4.210.10 YES NVRAM up up
Loopback0 192.122.3.10 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 172.19.102.10/25
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 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
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