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Table Of Contents
Configuration Register Information
Displaying the Configuration Register While Running Cisco IOS
Displaying the Configuration Register While Running ROM Monitor
Setting the Configuration Register While Running Cisco IOS
Setting the Configuration Register While Running ROM Monitor
Configuration Register Information
The following information is found in this appendix:
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Displaying the Configuration Register While Running Cisco IOS
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Configuration Bit Meanings
Use the processor configuration register information contained in this appendix to do the following:
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Table A-1 lists the meaning of each of the configuration memory bits. Following the table is a more in-depth description of each setting.
Bits 0-3
The lowest four bits of the processor configuration register (bits 3, 2, 1, and 0) form the boot field. Table A-2 provides information about the bits settings.
The boot field specifies a number in binary. If you set the boot field value to 0, you must have a console port access to boot the operating system manually. Boot the operating system by entering the b command at the bootstrap prompt as follows:
> b [tftp] flash filenameDefinitions of the various command options follow:
b—Boots the default system software from ROM
b flash—Boots the first file in Flash memory
b filename [host]—Boots over the network using TFTP
b flash filename—Boots the file (filename) from Flash memory
If you set the boot field value to a value of 2 through F, and there is a valid system boot command stored in the configuration file, the router boots the system software as directed by that value. (See Table A-3.) If you set the boot field to any other bit pattern, the router uses the resulting number to form a default boot filename for netbooting.
If there are no boot commands in the configuration file, the router attempts to boot the first file in system Flash memory. If no file is found in system Flash memory, the router attempts to netboot a default file with a name derived from the value of the boot field (for example, cisco2-7500). If the netboot attempt fails, the boot helper image in boot flash memory will boot up.
If boot commands are 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 the end of the list is reached without a file being successfully booted, the router will retry the netboot commands up to six times if bit 13 of the configuration register is set, otherwise it will load the operating system software available in ROMmon. If bit 13 is not set, the router will continue to netboot images indefinitely. The default setting for bit 13 is 0. If bit 13 is set, the system boots the boot helper image found in boot flash memory without any retries.
The server creates a default filename as part of the automatic configuration processes. To form the boot filename, the server starts with Cisco and links the octal equivalent of the boot field number, a dash, and the image name. Table A-3 lists the default boot filenames or actions.
Note
Bit 6
Bit 6 causes the system software to ignore nonvolatile random-access memory (NVRAM) contents.
Bit 7
Bit 7 enables the OEM bit. It disables the bootstrap messages at startup.
Bit 8
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 system into the bootstrap monitor, halting normal operation. A Break can be sent in the first sixty seconds while the system reboots, regardless of the configuration settings.
Bit 10 and Bit 14
Bit 10 controls the host portion of the Internet 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. B it 10 interacts with bit 14, which controls the network and subnet portions of the IP broadcast address. Table A-4 shows the combined effect of bit 10 and bit 14.
Table A-4 Bit 10 and Bit 14 Settings
Off
Off
<ones><ones>
Off
On
<zeros><zeros>
On
On
<net><zeros>
On
Off
<net><ones>
Bit 11 and Bit 12
Bit 11 and Bit 12 in the configuration register determine the baud rate of the console terminal. Table A-5 shows the bit settings for the four available baud rates. (The factory set default baud rate is 9600.)
Bit 13
Bit 13 determines the server response to a bootload failure. If boot commands are 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 the end of the list is reached without a file being successfully booted, the router will retry the netboot commands up to six times if bit 13 of the configuration register is set, otherwise it will load the operating system software available in ROMmon. If bit 13 is not set, the router will continue to netboot images indefinitely. The default setting for bit 13 is 0. If bit 13 is set, the system boots the boot helper image found in boot flash memory without any retries.
Bit 15
Bit 15 enables diagnostic messages and ignores NVRAM contents.
Displaying the Configuration Register While Running Cisco IOS
The configuration register can be viewed by using the show version or show hardware command.
The following is sample output of the show version command.
Router# show versionCisco Internetwork Operating System SoftwareIOS (tm) RSP Software (RSP-JSV-M), Version 12.0(10r)S1, EARLY DEPLOYMENTMAINTENANCE INTERIM SOFTWARETAC Support:http://www.cisco.com/cgi-bin/ibld/view.pl?i=supportCopyright (c) 1986-2002 by cisco Systems, Inc.Compiled Fri 22-Mar-02 16:27 by ninahungImage text-base:0x60010950, data-base:0x612A2000ROM:System Bootstrap, Version 12.0(10r)S1, RELEASE SOFTWARE (fc1)UUT uptime is 2 minutesSystem returned to ROM by reload at 15:33:45 UTC Tue Mar 5 2002System image file is "disk0:rsp-pv-mz.vip6-3.022802"cisco RSP4+ (R5000) processor with 65536K/2072K bytes of memory.R5000 CPU at 200Mhz, Implementation 35, Rev 2.1, 512KB L2 CacheLast reset from power-onG.703/E1 software, Version 1.0.G.703/JT2 software, Version 1.0.X.25 software, Version 3.0.0.1 VIP6 RM7000B controller (2 FastEthernet).1 GEIP controller (1 GigabitEthernet).2 FastEthernet/IEEE 802.3 interface(s)1 Gigabit Ethernet/IEEE 802.3 interface(s)123K bytes of non-volatile configuration memory.47040K bytes of ATA PCMCIA card at slot 0 (Sector size 512 bytes).16384K bytes of Flash internal SIMM (Sector size 256K).No slave installed in slot 7.Configuration register is 0x0Displaying the Configuration Register While Running ROM Monitor
If the bootstrap prompt ">", the o command displays the virtual configuration register currently in effect. It includes a description of the bits. See the following sample output:
>oConfiguration register + 02x100 at last bootBit# Configuration register option settings:15 Diagnostic mode disabled14 IP broadcasts do not have network numbers13 Boot default ROM software if network boot fails12-11 Console speed is 9600 baud10 IP broadcasts with ones09 Do not use secondary bootstrap08 Break disabled07 OEM disabled06 Ignore configuration disabled05 Fast boot disabled04 Fan boot disabled03-00 Boot to ROM monitorIf the prompt is "rommon1", the confreg command displays the virtual configuration register currently in effect. It includes a description of the bits. See the following sample output:
rommon 1 > confregConfiguration Summaryenabled are:load rom after netboot failsconsole baud: 9600boot: the ROM MonitorDo you wish to change the configuration? y/n [n]Setting the Configuration Register While Running Cisco IOS
The configuration register can be set in the configuration mode with the config-register 0x<value> command. See the following sample output:
Router# config tEnter configuration commands, one per line. End with CNTRL/Z.Router(config)#config-register 0x2142Router(config)#endRouter#%SYS-5-CONFIG_I: Configured from console by consoleSetting the Configuration Register While Running ROM Monitor
If the prompt is ">", the or0x<value> command sets the configuration register. See the following sample output:
>o/r 0x2102>If the prompt is "rommon1", the confreg command sets the configuration register. It prompts the user about each bit. See the following sample output:
rommon 1 > confregConfiuration Summaryenabled are:load rom after netboot failsconsole baud: 9600boot: the ROM Monitordo you wish to change the configuration y/n [n]: yenable "diagnostic mode"? y/n [n]: nenable "use net in IP bcast address"? y/n [n]: ndisable "use rom after netboot fails"? y/n [n]: nenable "use all zero broadcast"? y/n [n]: nenable "break/abort has effect"? y/n [n]: nenable "ignore system config info"? y/n [n]: nchange console baud rate? y/n [n]: nchange the boot characteristics? y/n [n]:yenter to boot:0 = ROM Monitor1 = the boot helper image2 - 15 = boot system[0]: 2Configuration Summary:enabled are:load rom after netboot failsconsole baud: 9600boot: image sepcified by the boot system commands or default to: cisco2-c7500do you wish to change the configuration? y/n [n] nYou must reset or power cycle for new config to take effectrommon 2 >
Posted: Thu Mar 24 12:03:07 PST 2005
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