Cisco Router 860, 880 Series User Manual
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B-11 Book Title OL-xxxxx-xx Appendix B Concepts Access Lists Access Lists With basic standard and static extended access lists, you can approximate session filtering by using the established keyword with the permit command. The established keyword filters TCP packets based on whether the ACK or RST bits are set. (Set ACK or RST bits indicate that the packet is not the first in the session and the packet therefore belongs to an established session.) This filter criterion would be part of an access list applied permanently to an interface.
B-12 Book Title OL-xxxxx-xx Appendix B Concepts Access Lists
C-1 Book Title OL-xxxxx-xx APPENDIXC ROM Monitor The ROM monitor firmware runs when the router is powered up or reset. The firmware helps to initialize the processor hardware and boot the operating system software. You can use the ROM monitor to perform certain configuration tasks, such as recovering a lost password or downloading software over the console port. If there is no Cisco IOS software image loaded on the router, the ROM monitor runs the router. This appendix contains the following sections: Entering the ROM Monitor, page C-1 ROM Monitor Commands, page C-2 Command Descriptions, page C-3 Disaster Recovery with TFTP Download, page C-3 Configuration Register, page C-6 Console Download, page C-7 Debug Commands, page C-8 Exiting the ROM Monitor, page C-10 Entering the ROM Monitor To use the ROM monitor, you must be using a terminal or PC that is connected to the router over the console port. Perform these steps to configure the router to boot up in ROM monitor mode the next time it is rebooted. CommandPurpose Step 1enableEnters privileged EXEC mode. Enter your password if prompted. Step 2configure terminalEnters global configuration mode. Step 3config-reg 0x0Resets the configuration register.
C-2 Book Title OL-xxxxx-xx Appendix C ROM Monitor ROM Monitor Commands TimesaverBreak (system interrupt) is always enabled for 60 seconds after the router reboots, regardless of whether it is set to on or off in the configuration register. During this 60-second window, you can break to the ROM monitor prompt by pressing the Break key. ROM Monitor Commands Enter ? or help at the ROM monitor prompt to display a list of available commands and options, as follows: rommon 1 > ?alias set and display aliases command boot boot up an external process break set/show/clear the breakpointconfreg configuration register utility cont continue executing a downloaded image context display the context of a loaded image cookie display contents of cookie PROM in hexcopy Copy a file-copy [-b ] delete Delete file(s)-delete dir List files in directories-dir dis display instruction stream dnld serial download a program module format Format a filesystem-format frame print out a selected stack frame fsck Check filesystem consistency-fsck help monitor builtin command helphistory monitor command history meminfo main memory information mkdir Create dir(s)-mkdir more Concatenate (type) file(s)-cat rename Rename a file-rename repeat repeat a monitor commandreset system reset rmdir Remove a directory set display the monitor variablesstack produce a stack trace sync write monitor environment to NVRAM sysret print out info from last system returntftpdnld tftp image download unalias unset an alias unset unset a monitor variablexmodem x/ymodem image download Step 4exitExits global configuration mode. Step 5reloadReboots the router with the new configuration register value. The router remains in ROM monitor and does not boot the Cisco IOS software. As long as the configuration value is 0x0, you must manually boot the operating system from the console. See the boot command in the “ Command Descriptions” section in this appendix. After the router reboots, it is in ROM monitor mode. The number in the prompt increments with each new line. Command Purpose
C-3 Book Title OL-xxxxx-xx Appendix C ROM Monitor Command Descriptions Commands are case sensitive. You can halt any command by pressing the Break key on a terminal. If you are using a PC, most terminal emulation programs halt a command when you press the Ctrl and the Break keys at the same time. If you are using another type of terminal emulator or terminal emulation software, see the documentation for that product for information on how to send a Break command. Command Descriptions Ta b l e C-1 describes the most commonly used ROM monitor commands. Disaster Recovery with TFTP Download The standard way to load new software on your router is to use the copy tftp flash privileged EXEC command from the Cisco IOS software command-line interface (CLI). However, if the router is unable to boot Cisco IOS software, you can load new software while in ROM monitor mode. This section describes how to load a Cisco IOS software image from a remote TFTP server to the router flash memory. Use the tftpdnld command only for disaster recovery, because it erases all existing data in flash memory before downloading a new software image to the router. Ta b l e C-1 Commonly Used ROM Monitor Commands CommandDescription help or ?Displays a summary of all available ROM monitor commands. -?Displays information about command syntax; for example: rommon 16 > dis -?usage : dis [addr] [length] The output for this command is slightly different for the xmodem download command: rommon 11 > xmodem -? xmodem: illegal option -- ? usage: xmodem [-cyrxu] -c CRC-16 -y ymodem-batch protocol -r copy image to dram for launch-x do not launch on download completion -u upgrade ROMMON, System will reboot after upgrade reset or iResets and initializes the router, similar to a power up. dir device:Lists the files on the named device; for example, flash memory files: rommon 4 > dir flash: Directory of flash:/2 -rwx 10283208 c880-advsecurityk9-mz 9064448 bytes available (10289152 bytes used) boot commandsFor more information about the ROM monitor boot commands, see the Cisco IOS Configuration Fundamentals and Network Management Guide. bBoots the first image in flash memory. b flash: [filename]Attempts to boot the image directly from the first partition of flash memory. If you do not enter a filename, this command will boot this first image in flash memory.
C-4 Book Title OL-xxxxx-xx Appendix C ROM Monitor Disaster Recovery with TFTP Download TFTP Download Command Variables This section describes the system variables that can be set in ROM monitor mode and that are used during the TFTP download process. There are both required variables and optional variables. NoteThe commands described in this section are case sensitive and must be entered exactly as shown. Required Variables These variables must be set with these commands before you use the tftpdnld command: VariableCommand IP address of the router.IP_ADDRESS= ip_address Subnet mask of the router.IP_SUBNET_MASK= ip_address IP address of the default gateway of the router.DEFAULT_GATEWAY= ip_address IP address of the TFTP server from which the software will be downloaded.TFTP_SERVER= ip_address Name of the file that will be downloaded to the router.TFTP_FILE= filename
C-5 Book Title OL-xxxxx-xx Appendix C ROM Monitor Disaster Recovery with TFTP Download Optional Variables These variables can be set with these commands before using the tftpdnld command: Using the TFTP Download Command To download a file through TFTP perform these steps in ROM monitor mode Step 1Use the appropriate commands to enter all the required variables and any optional variables described in preceding sections. Step 2Enter the tftpdnld command as follows: rommon 1 > tftpdnld -r NoteThe -r variable is optional. Entering this variable downloads and boots the new software but does not save the software to flash memory. You can then use the image that is in flash memory the next time you enter the reload command. VariableCommand Configures how the router displays file download progress. 0—No progress is displayed. 1—Exclamation points (!!!) are displayed to indicate file download progress. This is the default setting. 2—Detailed progress is displayed during the file download process; for example: Initializing interface. Interface link state up. ARPing for 1.4.0.1 ARP reply for 1.4.0.1 received. MAC address 00:00:0c:07:ac:01 TFTP_VERBOSE= setting Number of times the router attempts ARP and TFTP download. The default is 7. TFTP_RETRY_COUNT= retry_times Length of time, in seconds, before the download process times out. The default is 2,400 seconds (40 minutes). TFTP_TIMEOUT= time Whether or not the router performs a checksum test on the downloaded image: 1—Checksum test is performed. 0—No checksum test is performed. TFTP_CHECKSUM=setting
C-6 Book Title OL-xxxxx-xx Appendix C ROM Monitor Configuration Register You will see output similar to the following: IP_ADDRESS: 10.3.6.7 IP_SUBNET_MASK: 255.255.0.0DEFAULT_GATEWAY: 10.3.0.1 TFTP_SERVER: 192.168.254.254 TFTP_FILE: c880-advsecurityk9-mzDo you wish to continue? y/n: [n]: Step 3If you are sure that you want to continue, enter y in response to the question in the output: Do you wish to continue? y/n: [n]:y The router begins to download the new file. If you mistakenly entered yes, you can enter Ctrl-C or Break to stop the transfer before the flash memory is erased. Configuration Register The virtual configuration register is in nonvolatile RAM (NVRAM) and has the same functionality as other Cisco routers. You can view or modify the virtual configuration register from either the ROM monitor or the operating system software. Within the ROM monitor, you can change the configuration register by entering the register value in hexadecimal format, or by allowing the ROM monitor to prompt you for the setting of each bit. Changing the Configuration Register Manually To change the virtual configuration register from the ROM monitor manually, enter the confreg command followed by the new value of the register in hexadecimal format, as shown in the following example: rommon 1 > confreg 0x2101 You must reset or power cycle for new config to take effect rommon 2 > The value is always interpreted as hexadecimal. The new virtual configuration register value is written into NVRAM but does not take effect until you reset or reboot the router. Changing the Configuration Register Using Prompts Entering the confreg command without an argument displays the contents of the virtual configuration register and a prompt to alter the contents by describing the meaning of each bit. In either case, the new virtual configuration register value is written into NVRAM but does not take effect until you reset or reboot the router.
C-7
Book Title
OL-xxxxx-xx
Appendix C ROM Monitor
Console Download
The following display shows an example of entering the confreg command:
rommon 7> confreg
Configuration Summary
enabled are:
console baud: 9600boot: the ROM Monitor
do you wish to change the configuration? y/n [n]: yenable “diagnostic mode”? y/n [n]: y
enable “use net in IP bcast address”? y/n [n]:
enable “load rom after netboot fails”? y/n [n]: enable “use all zero broadcast”? y/n [n]:
enable “break/abort has effect”? y/n [n]:
enable “ignore system config info”? y/n [n]: change console baud rate? y/n [n]: y
enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400 [0]: 0
change the boot characteristics? y/n [n]: yenter to boot:
0 = ROM Monitor
1 = the boot helper image 2-15 = boot system
[0]: 0
Configuration Summaryenabled are:
diagnostic mode
console baud: 9600boot: the ROM Monitor
do you wish to change the configuration? y/n [n]:
You must reset or power cycle for new config to take effect
Console Download
You can use console download, which is a ROM monitor function, to download either a software image
or a configuration file over the router console port. After download, the file is either saved to the
mini-flash memory module or to main memory for execution (image files only).
Use console download when you do not have access to a TFTP server.
NoteIf you want to download a software image or a configuration file to the router over the console port, you
must use the ROM monitor dnld command.
NoteIf you are using a PC to download a Cisco IOS image over the router console port at 115,200 bps, ensure
that the PC serial port is using a 16550
universal asynchronous transmitter/receiver (UART). If the PC
serial port is not using a 16550
UART, we recommend using a speed of 38,400 bps or less when
downloading a Cisco IOS image over the console port.
C-8 Book Title OL-xxxxx-xx Appendix C ROM Monitor Debug Commands Command Description The following are the syntax and descriptions for the xmodem console download command: xmodem [-cyrx] destination_file_name Follow these steps to run Xmodem: Step 1Move the image file to the local drive where Xmodem will execute. Step 2Enter the xmodem command. Error Reporting Because the ROM monitor console download uses the console to perform the data transfer, when an error occurs during a data transfer, error messages are only displayed on the console once the data transfer is terminated. If you have changed the baud rate from the default rate, the error message is followed by a message telling you to restore the terminal to the baud rate specified in the configuration register. Debug Commands Most ROM monitor debugging commands are functional only when Cisco IOS software has crashed or is halted. If you enter a debugging command and Cisco IOS crash information is not available, you see the following error message: xxx: kernel context state is invalid, can not proceed. cOptional. Performs the download using 16-bit cyclic redundancy check (CRC-16) error checking to validate packets. Default is 8-bit CRC. yOptional. Sets the router to perform the download using Ymodem protocol. The default is Xmodem protocol. The protocols differ as follows: Xmodem supports a 128-block transfer size. Ymodem supports a 1024-block transfer size. Ymodem uses CRC-16 error checking to validate each packet. Depending on the device that the software is being downloaded from, this function might not be supported by Xmodem. rOptional. Image is loaded into DRAM for execution. The default is to load the image into flash memory. xOptional. Image is loaded into DRAM without being executed. destination_ file_nameName of the system image file or the system configuration file. In order for the router to recognize it, the name of the configuration file must be router_confg.