Cisco IOS Configuration Fundamentals Command Reference

Cisco IOS Configuration Commands

To display the internal components of the router use the command Show Version, this command will show the Cisco IOS configuration version running on the router device, configuration register, memory, number of interfaces, and device model.

To display the contents and layout of a Flash memory file system, use the command show flash in EXEC mode. This command will show the information of System Flash Directory including File name, length, and IOS Status.

Cisco IOS Configuration

1. System flash Checking

Router> enable

Router# configure terminal

Enter configuration commands, one per line. End with CNTL / Z.

Router (config) # hostname R1

R1 (config) # exit

R1# show flash:

System flash directory:

File Length Name / Status

1 16299836 2600 source ios

(Total bytes 33030140, bytes used 16299900, available bytes 16730240)

(Processor board System flash (Read / Write) bytes 32768K)

2. Configuration Register’s Value and IOS Version

In NVRAM the router has a 16-bit configuration and to perform the below tasks you can use the configuration register.

v Load operating software from ROM
v Lost password Recovery
v Console data rate change
v Force the router into the RAM monitor (bootstrap program)
v Boot source and default boot filename selection
v Break function enable / disable

0-3 bits of the configuration register form the boot field and these four bits are the lowest bits. In the configuration register setting the router/switch looks for system bootstrap information depending on the boot field. The system ignores any boot instruction in the system configuration file when the field is set to either 0 or 1 (0-0-0-0 or 0-0-0-1) and the following occurs:

v Boot the operating system manually by giving a boot command to the ROM monitor, or to the system bootstrap program when the boot field is set to 0.

v Boot from the IOS image stored in ROM when the boot field is set to 1.