Router LED indicators/The initial router bootup

Router LED indicators
2.2.2 This page will explain how routers use LED indicators.


Cisco routers use LED indicators to provide status information. LED indicators will vary for different Cisco router models.

An interface LED indicates the activity of the corresponding interface. A problem may be indicated if an LED is off when the interface is active and the interface is correctly connected. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly.

The next page will examine the initial router bootup

The initial router bootup
2.2.3 This page will discuss the information and messages that are displayed during the initial router bootup. This information will vary, depending on the interfaces in the router and the Cisco IOS release. The screens displayed on this page are for reference only and may not reflect what the screen displays on the console.


In Figure , the statement “NVRAM invalid, possibly due to write erase”, tells the user that this router has not been configured yet or that the NVRAM has been erased. In order for the NVRAM to be valid after a router is configured and the configuration file is saved to NVRAM, the router must be configured to use the NVRAM configuration file. The factory-default setting for the configuration register is 0x2102, which indicates that the router should attempt to load a Cisco IOS image from flash memory.

In Figure , the user can determine the bootstrap version and the IOS version the router is using as well as the router model, processor, and the amount of memory the router contains. The figure also includes the following information:

• The number of interfaces
• The types of interfaces
• The amount of NVRAM
• The amount of flash memory

In Figure , the user has the option to enter setup mode. Remember, the primary purpose of the setup mode is to permit an administrator to install a basic router configuration when it cannot be obtained from another source.

The next page will teach students how to establish a console session with a router.