Cisco 2921 User Manual

C-13
Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
Appendix C Using ROM Monitor
How to Use the ROM Monitor—Typical Tasks
Modifying the Configuration Register (confreg)
This section describes how to modify the configuration register by using the confreg ROM monitor
command. You can also modify the configuration register setting from the Cisco IOS command-line
interface (CLI) by using the config-register command in global configuration mode.
Caution Do not set the configuration register by using the config-register 0x0 command after setting the baud
rate. To set the configuration register without affecting the baud rate, use the current configuration
register setting by entering the show ver | inc configuration command and then replacing the last
(rightmost) number with a 0 in the configuration register command.
Restrictions
The modified configuration register value is automatically written into NVRAM, but the new value does
not take effect until you reset or power-cycle the router.
SUMMARY STEPS
1. confreg [value]
DETAILED STEPS
Examples
In the following example, the configuration register is set to boot the system image from flash memory:
rommon 3 > confreg 0x2102
In the following example, no value is entered; therefore, the system prompts for each bit in the register:
rommon 7 > confreg
Configuration Summary
enabled are:
console baud: 9600
boot: the ROM Monitor
do you wish to change the configuration? y/n [n]: y
enable "diagnostic mode"? y/n [n]: y
enable "use net in IP bcast address"? y/n [n]: y
enable "load rom after netboot fails"? y/n [n]: y
enable "use all zero broadcast"? y/n [n]: y
enable "break/abort has effect"? y/n [n]: y
Command or Action Purpose
Step 1
confreg [value]
Example:
rommon > confreg 0x2102
Changes the configuration register settings while in ROM
monitor mode.
• Optionally, enter the new hexadecimal value for the
configuration register. The value range is from 0x0 to
0xFFFF.
• If you do not enter the value, the router prompts for
each bit of the 16-bit configuration register.

Cisco 2921 Specifications

General

Ethernet LAN	Yes
Cabling technology	10/100/1000Base-T(X)
Networking standards	IEEE 802.1Q, IEEE 802.1ag, IEEE 802.3, IEEE 802.3ab, IEEE 802.3af, IEEE 802.3ah, IEEE 802.3u
Ethernet LAN data rates	10, 100, 1000 Mbit/s
Ethernet interface type	Gigabit Ethernet
Product color	Black
Rack capacity	2U
USB version	2.0
RS-232 ports	1
USB ports quantity	2
Ethernet LAN (RJ-45) ports	3
DHCP client	-
Routing protocols	BGP, EIGRP, OSPF
Supported protocols	IPv4, IPv6, IS-IS, IGMPv3, PIM SM, SSM, DVMRP, IPSec, GRE, BVD, MPLS, L2TPv3, PPP, MLPPP, MLFR, HDLC, RS-232, RS-449, X.21, V.35, EIA-530, PPPoE, ATM
Firewall security	Cisco IOS
Operating altitude	0 - 3000 m
Non-operating altitude	0 - 4570 m
Storage temperature (T-T)	-40 - 70 °C
Operating temperature (T-T)	0 - 40 °C
Storage relative humidity (H-H)	5 - 95 %
Operating relative humidity (H-H)	10 - 85 %
AC input voltage	100 - 240 V
Power source type	AC
AC input frequency	47 - 63 Hz
Safety	UL 60950-1, CAN/CSA C22.2 No. 60950-1, EN 60950-1, AS/NZS 60950-1, IEC 60950-1
Electromagnetic compatibility	47 CFR, ICES-003, EN55022, CISPR22, AS/NZS 3548, VCCI V-3, EN 300-386, EN 61000, EN 55024, CISPR 24EN50082-1

Weight and Dimensions

Depth	469.9 mm
Width	438.2 mm
Height	88.9 mm
Weight	13200 g