Cisco Systems 2600 manual Bit Address net host

Appendix C Configuration Register

Configuring the Boot Field

The boot field specifies a number in binary form. If you set the boot field value to 0, you must have console port access to boot the operating system manually. Refer to the boot command in the “ROM Monitor Command Descriptions” section on page B-4.

If you set the boot field to a value of 2 to F, and there is a valid boot system command stored in the configuration file, the router software processes each boot command in sequence until the process is successful or the end of the list is reached. If there are no boot commands in the configuration file, the router attempts to boot the first file in flash memory.

In the following example, the configuration register is set to boot the router automatically from flash memory and to ignore Break at the next reboot of the router:

Router# configure terminal

Enter configuration commands, one per line.

Edit with DELETE, CTRL/W, and CTRL/U; end with CTRL/Z config-register 0x102

Ctrl-z

Note A boot system command in the router configuration in NVRAM overrides booting from flash memory.

Bit 8 controls the console Break key. Setting bit 8 (the factory default) causes the processor to ignore the console Break key. Clearing bit 8 causes the processor to interpret Break as a command to force the router into the bootstrap monitor, halting normal operation. Break can always be sent in the first

60 seconds while the router is rebooting, regardless of the configuration settings.

Bit 9 controls the system boot. Clearing bit 9 (the factory default) causes the system to boot from flash memory. Clearing bit 9 causes the system to use the secondary bootstrap (netbooting). This is typically not used.

Bit 10 controls the host portion of the IP broadcast address. Setting bit 10 causes the processor to use all zeros; clearing bit 10 (the factory default) causes the processor to use all ones. Bit 10 interacts with bit 14, which controls the network and subnet portions of the broadcast address. Table C-3shows the combined effect of bit 10 and bit 14.

Table C-3 Configuration Register Settings for Broadcast Address Destination

Bit 10	Bit 14	Address (<net> <host>)
Off	Off	<ones> <ones>
On	Off	<zeros> <zeros>
On	On	<net> <zeros>
Off	On	<net> <ones>

Bit 13 determines the router’s response to a bootload failure. Setting bit 13 causes the router to load operating software from ROM after six unsuccessful attempts to load a boot file. Clearing bit 13 causes the router to continue indefinitely to attempt loading a boot file. By factory default, bit 13 is set to 0.

Bit 5, bit 11, and bit 12 of the configuration register determine the baud rate of the console terminal. Table C-4shows the bit settings for the eight available rates. (The default baud rate is 9600 bps.)

Cisco 2600 Series Routers Hardware Installation Guide

C-4 OL-2171-06