This document provides the following information:
Use the processor configuration register information contained in this section to do the following:
Bit Number | Hex | Meaning |
---|---|---|
00–03 |
0x0000–0x000F |
Boot field |
06 |
0x0040 |
Causes the system software to ignore nonvolatile random-access memory (NVRAM) contents |
07 |
0x0080 |
OEM (original equipment manufacturer) bit enabled |
08 |
0x0100 |
Break disabled |
10 |
0x0400 |
IP broadcast with all zeros |
11–12 |
0x800–0x1000 |
Console line speed |
13 |
0x2000 |
Boots default ROM software if initial boot fails |
14 |
0x4000 |
IP broadcasts do not have network numbers |
15 |
0x8000 |
Enables diagnostic messages and ignores NVRAM contents |
The lowest four bits of the processor configuration register (bits 3, 2, 1, and 0) form the boot field.
Boot Field | Meaning |
---|---|
0 |
Stays at the system bootstrap prompt (ROM monitor) on a reload or power cycle |
1 |
Boots the boot helper image as a system image |
2 |
Full boot process, which loads the Cisco IOS image into Flash memory |
2-F |
Specifies a default filename for booting over the network from a TFTP server |
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 filename
Definitions 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 2) 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, cisco2-7200). 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.
![]() Note | A boot system configuration command in the router configuration in NVRAM overrides the default netboot filename. |
Action/File Name | Bit 3 | Bit 2 | Bit 1 | Bit 0 |
---|---|---|---|---|
Bootstrap mode |
0 |
0 |
0 |
0 |
ROM software |
0 |
0 |
0 |
1 |
Flash software |
0 |
0 |
1 |
0 |
cisco3-< image-name1> |
0 |
0 |
1 |
1 |
cisco4-<image-name2> |
0 |
1 |
0 |
0 |
cisco5-<image-name3> |
0 |
1 |
0 |
1 |
cisco6-<image-name4> |
0 |
1 |
1 |
0 |
cisco7-<image-name5> |
0 |
1 |
1 |
1 |
cisco10-<image-name6> |
1 |
0 |
0 |
0 |
cisco11-<image-name7> |
1 |
0 |
0 |
1 |
cisco12-<image-name8> |
1 |
0 |
1 |
0 |
cisco13-<image-name9> |
1 |
0 |
1 |
1 |
cisco14-<image-name10> |
1 |
1 |
0 |
0 |
cisco15-<image-name11> |
1 |
1 |
0 |
1 |
cisco16-<image-name12> |
1 |
1 |
1 |
0 |
cisco17-<image-name13> |
1 |
1 |
1 |
1 |
Bit 6 causes the system software to ignore nonvolatile random-access memory (NVRAM) contents.
Bit 7 enables the OEM bit. It disables the bootstrap messages at startup.
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 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. The table below shows the combined effect of bit 10 and bit 14:
Bit 14 | Bit 10 | IP Address (<net> <host>) |
---|---|---|
Off |
Off |
<ones><ones> |
Off |
On |
<zeros><zeros> |
On |
On |
<net><zeros> |
On |
Off |
<net><ones> |
![]() Note | The console line rate on Cisco universal broadband routers is fixed at 9600 and cannot be changed. For more information about configuring baud rates, see Appendix B: Cisco CMTS Router ROM Monitor Commands in the Cisco IOS CMTS Cable Command Reference . |
Bit 11 and Bit 12 in the configuration register determine the baud rate of the console terminal. The table below shows the bit settings for the four available baud rates (the factory set default baud rate is 9600):
Baud | Bit 12 | Bit 11 |
---|---|---|
9600 |
0 |
0 |
4800 |
0 |
1 |
2400 |
1 |
1 |
1200 |
1 |
0 |
![]() Note | The console line rate on Cisco universal broadband routers is fixed at 9600 and cannot be changed. For more information about configuring baud rates, see Appendix B: Cisco CMTS Router ROM Monitor Commands in the Cisco IOS CMTS Cable Command Reference . |
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 enables diagnostic messages and ignores NVRAM contents.
This section provides examples for displaying the configuration register for while running Cisco IOS on Cisco uBR10012 and Cisco uBR7200 series routers.
The configuration register can be viewed by using the show version or show hardware command.
The following example illustrates output from the show version command for a Cisco uBR10012 router with the Cisco OC-48 DPT/POS interface module in POS mode:
Router# show version Cisco Internetwork Operating System Software IOS (tm) 10000 Software (UBR10K-K8P6-M), Experimental Version 12.2(20021115:194156) [REL-ftp_p2_clip per_srp.ios-weekly 103] Copyright (c) 1986-2002 by cisco Systems, Inc. Compiled Fri 15-Nov-02 18:05 by richv Image text-base: 0x60008940, data-base: 0x61A80000 ROM: System Bootstrap, Version 12.0(9r)SL2, RELEASE SOFTWARE (fc1) R7582-ubr10k-UUT uptime is 10 hours, 14 minutes System returned to ROM by power-on System image file is "bootflash:ubr10k-k8p6-mz.oc48.15Nov02" cisco uBR10012 (PRE1-RP) processor with 393215K/131072K bytes of memory. Processor board ID TBA05080267 R7000 CPU at 262Mhz, Implementation 39, Rev 2.1, 256KB L2, 2048KB L3 Cache Backplane version 1.0, 8 slot Last reset from power-on Toaster processor tmc0 is running. Toaster processor tmc1 is running. 1 OC12 POS controller (1 POS) 1 TCCplus card(s) 1 FastEthernet/IEEE 802.3 interface(s) 1 Gigabit Ethernet/IEEE 802.3 interface(s) 3 Packet over SONET network interface(s) 2 Cable Modem network interface(s) 509K bytes of non-volatile configuration memory. 46976K bytes of ATA PCMCIA card at slot 0 (Sector size 512 bytes). 32768K bytes of Flash internal SIMM (Sector size 256KB). Configuration register is 0x0 Router#
The configuration register can be viewed by using the show version or show hardware command.
The following example illustrates output from the show version command for a Cisco uBR7246 VXR router with the cable clock card installed:
Router# show version Cisco Internetwork Operating System Software IOS (tm) 7200 Software (UBR7200-P-M), Version 12.1(10)EC, RELEASE SOFTWARE TAC Support: http://www.cisco.com/tac Copyright (c) 1986-2000 by cisco Systems, Inc. Compiled Wed 02-Feb-00 16:49 by ccai Image text-base:0x60008900, data-base:0x61192000 ROM:System Bootstrap, Version 12.0(15)SC, RELEASE SOFTWARE VXR1 uptime is 2 days, 1 hour, 24 minutes System returned to ROM by power-on at 10:54:38 PST Sat Feb 5 2000 System restarted at 11:01:08 PST Sat Feb 5 2000 System image file is "slot1:ubr7200-p-mz.121-0.8.T" cisco uBR7246VXR (NPE300) processor (revision B) with 122880K/40960K bytes of memory. Processor board ID SAB0329005N R7000 CPU at 262Mhz, Implementation 39, Rev 1.0, 256KB L2, 2048KB L3 Cache 6 slot VXR midplane, Version 2.0 Last reset from power-on X.25 software, Version 3.0.0. National clock card with T1 controller 1 FastEthernet/IEEE 802.3 interface(s) 2 Cable Modem network interface(s) 125K bytes of non-volatile configuration memory. 16384K bytes of Flash PCMCIA card at slot 0 (Sector size 128K). 20480K bytes of Flash PCMCIA card at slot 1 (Sector size 128K). 4096K bytes of Flash internal SIMM (Sector size 256K). Configuration register is 0x0 Router#
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:
>o Configuration register + 02x100 at last boot Bit# Configuration register option settings: 15 Diagnostic mode disabled 14 IP broadcasts do not have network numbers 13 Boot default ROM software if network boot fails 12-11 Console speed is 9600 baud 10 IP broadcasts with ones 09 Do not use secondary bootstrap 08 Break disabled 07 OEM disabled 06 Ignore configuration disabled 05 Fast boot disabled 04 Fan boot disabled 03-00 Boot to ROM monitor
If 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 > confreg Configuration Summary enabled are: load rom after netboot fails console baud: 9600 boot: the ROM Monitor Do you wish to change the configuration? y/n [n]
The configuration register can be set in the configuration mode with the config-register 0x value command. See the following sample output:
Router# configure terminal Enter configuration commands, one per line. End with CNTRL/Z. Router(config)# config-register 0x2142 Router(config)# end Router# %SYS-5-CONFIG_I: Configured from console by console
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 > confreg Confiuration Summary enabled are: load rom after netboot fails console baud: 9600 boot: the ROM Monitor do you wish to change the configuration y/n [n]: y enable “diagnostic mode”? y/n [n]: n enable “use net in IP bcast address”? y/n [n]: n disable “use rom after netboot fails”? y/n [n]: n enable “use all zero broadcast”? y/n [n]: n enable “break/abort has effect”? y/n [n]: n enable “ignore system config info”? y/n [n]: n change console baud rate? y/n [n]: n change the boot characteristics? y/n [n]:y enter to boot: 0 = ROM Monitor 1 = the boot helper image 2 - 15 = boot system [0]: 2 Configuration Summary: enabled are: load rom after netboot fails console baud: 9600 boot: image sepcified by the boot system commands or default to: cisco2-c7200 do you wish to change the configuration? y/n [n] n You must reset or power cycle for new config to take effect rommon 2 >