Status message of Interfaces On router

When we use “Show Interfaces” command on router. The first two lines will display the status message. It will display one of the following four messages.

Interface is administratively down, line protocol is down.

This message means that the interface is shutdown by the administrator using “shutdown” command. We can change this status with help of “no shutdown” command.

Interface is up, line protocol is up.

This message will appear when everything working fine and interface is able to communicate with other devices. In case of Ethernet, this message will display when  interface is connected and enabled. In case of serial, this message will display when end to end connectivity is established.

Interface is down, line protocol is down

This message will appear in case of serial interface when the other router’s interface is administratively shutdown. This message will never appear in case of Ethernet.

Interface is up, line protocol is down

This message will appear on serial due to the clock rate not set and encapsulation failure. In case of Ethernet, this message may appear when interface is not connected properly. In case of serial, this message may appear due to following  

   R ----------M----------------M------x------x R

                                                Fault

e.g:-
router#show Interface serial 0

router#show Interface eth 0

Router Booting Sources :- A router can boot from various sources. By default, it will boot from the flash memory and we can control the sequence with the help of configuration system or commands. A router can boot from following sources: - 

1. First file in flash
2. Specific file in flash
3. Incomplete IOS
4. TFTP Server
5. Rom Monitor (from Bios)

The first to control boot sequence using configuration system register. We can modify configuration register value with the help of “config-register” command in global configuration mode. We can also modify register value from ROM monitor mode.

Configuration Register :-- Configuration Register is 16-bit value, which is stored in the NVRAM. At the time of booting the Bootstrap Loader reads the value of configuration Register and according to the value it configure its booting behavior.

0x2102 (IOS with Config)

With this value the router will boot from first file present in the flash memory. This is the default value of configuration register. After loading IOS the router will also load startup-config config into running-config.

0x2101 (Incomplete IOS with Config)

The router will boot from incomplete IOS and then load the startup-config.

0x2100 (Rom Monitor)

With this router will not boot. But enters to the Rom Monitor mode.

0x2142 (IOS without Config)

The router will boot from first file in flash. But bypass the startup configuration

0x2141 (Incomplete IOS without Config)

The router will boot from Incomplete IOS but bypass the startup-config.

To change Config-Register from global mode 

Router#configure terminal

Router(config)#config-register <value>

Router(config)#exit

Router#reload

Note: - this is the only value, which is configured in the configuration mode and does not need to be saved.

To change Config-Register using Rom Monitor 
 Steps: - 

1.  Power on the router 
2.  Press “ctrl+break” from console with in 60 sec. 
3.  The router will enter to the Rom Monitor. Type following commands Rom Mon>confreg <value>  & Rom Mon>i

Note: - in 2500 series router “o/r” command should be used in place of “confreg” command. 
Boot System commands:- Boot system command is the second method to control sequence of router. These commands will be executed only when configuration register is set to 0x2102.

Boot system commands are executed in global configuration mode. These commands are executed in the same sequence they are applied to the router. If one boot system command is successful then next boot system command is not executed in the router.

Router(config)#boot system flash <file name>

To boot router from specific file in flash

Router(config)#boot system tftp <file name> <IP address>

To boot router from TFTP server/network

Router(config)#boot system flash

To boot from first file in flash

Router(config)#boot system rom

To boot from incomplete IOS

Posted in: CCNA