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Appendix B      ROM Monitor
Debug Commands
context—displays processor context; for example:
rommon 7> context
CPU context of the most recent exception:
PC  = 0x801111b0  MSR = 0x00009032  CR  = 0x53000035  LR    = 
0x80113694
CTR = 0x801065e4  XER = 0xa0006d36  DAR = 0xffffffff  DSISR = 
0xffffffff
DEC = 0xffffffff  TBU = 0xffffffff  TBL = 0xffffffff  IMMR  = 
0xffffffff
R0  = 0x00000000  R1  = 0x80005ea8  R2  = 0xffffffff  R3    = 
0x00000000
R4  = 0x8fab0d76  R5  = 0x80657d00  R6  = 0x80570000  R7    = 
0x80570000
R8  = 0x00000000  R9  = 0x80570000  R10 = 0x0000954c  R11   = 
0x00000000
R12 = 0x00000080  R13 = 0xffffffff  R14 = 0xffffffff  R15   = 
0xffffffff
R16 = 0xffffffff  R17 = 0xffffffff  R18 = 0xffffffff  R19   = 
0xffffffff
R20 = 0xffffffff  R21 = 0xffffffff  R22 = 0xffffffff  R23   = 
0xffffffff
R24 = 0xffffffff  R25 = 0xffffffff  R26 = 0xffffffff  R27   = 
0xffffffff
R28 = 0xffffffff  R29 = 0xffffffff  R30 = 0xffffffff  R31   = 
0xffffffff
frame—displays an individual stack frame. 
sysret—displays return information from the last booted system image. This 
information includes the reason for terminating the image, a stack dump of 
up to eight frames, and, if an exception is involved, the address where the 
exception occurred; for example:
rommon 8> sysret
System Return Info:
count: 19,  reason: user break
pc:0x801111b0,  error address: 0x801111b0
Stack Trace:
FP: 0x80005ea8, PC: 0x801111b0
FP: 0x80005eb4, PC: 0x80113694
FP: 0x80005f74, PC: 0x8010eb44
FP: 0x80005f9c, PC: 0x80008118
FP: 0x80005fac, PC: 0x80008064
FP: 0x80005fc4, PC: 0xfff03d70
FP: 0x80005ffc, PC: 0x00000000
FP: 0x00000000, PC: 0x00000000 
						

							 
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meminfo—displays size in bytes, starting address, available range of main 
memory, the starting point and size of packet memory, and size of NVRAM; 
for example:
rommon 9> meminfo
Main memory size: 40 MB.
Available main memory starts at 0x10000, size 40896KB
IO (packet) memory size: 5 percent of main memory.
NVRAM size: 32KB
Disaster Recovery with Console Download of Cisco 
IOS Software
You can use console download, a ROM monitor function, to download over the 
router console port either a software image or a configuration file. Make sure that 
the Cisco IOS image is in the same PC where you are to perform this function. 
After downloading, the file is saved either 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 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 UART. If the PC 
serial port is not using a 16550 UART, we recommend using a speed of 38,400 or 
less when downloading a Cisco IOS image over the console port.
Command Description
Following are the syntax and descriptions for the xmodem console download 
command:
xmodem [-cyrx] destination_file_name 
						

							 
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Appendix B      ROM Monitor
Disaster Recovery with Console Download of Cisco IOS Software
Follow the steps below to run Xmodem:
1.Move the image file to the local drive where the Xmodem will execute. 
2.Enter the xmodem command.
Error Reporting
Because the ROM monitor console download uses the console to perform the data 
transfer, error messages are displayed on the console only when the data transfer 
is terminated. 
If an error does occur during a data transfer, the transfer is terminated, and an 
error message is displayed. 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. 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. 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. Default 
is to load the image into Flash memory.
xOptional. Image is loaded into DRAM without being executed.
destination_
file_nameThe name 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. 
						

							 
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Debug Commands
Most ROM monitor debugging commands are functional only when the 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, cannot proceed.”
The following are ROM monitor debugging commands:
stack or k—produce a stack trace; for example:
rommon 6 > stack
Stack trace:
PC = 0x801111b0
Frame 00: FP = 0x80005ea8 PC = 0x801111b0
Frame 01: FP = 0x80005eb4 PC = 0x80113694
Frame 02: FP = 0x80005f74 PC = 0x8010eb44
Frame 03: FP = 0x80005f9c PC = 0x80008118
Frame 04: FP = 0x80005fac PC = 0x80008064
Frame 05: FP = 0x80005fc4 PC = 0xfff03d70
context—displays processor context; for example:
rommon 7> context
CPU context of the most recent exception:
PC = 0x801111b0 MSR = 0x00009032 CR = 0x53000035 LR =
0x80113694
CTR = 0x801065e4 XER = 0xa0006d36 DAR = 0xffffffff DSISR =
0xffffffff
DEC = 0xffffffff TBU = 0xffffffff TBL = 0xffffffff IMMR =
0xffffffff
RO = 0x00000000 R1 = 0x80005ea8 R2 = oxffffffff R3 =
0x00000000
R4 = 0x8fab0d76 R5 = 0x80657d00 R6 = 0x80570000 R7 =
0x80570000
R8 = 0x00000000 R9 = 0x80570000 R10 =0x0000954c R11=
0x00000000
R12 = 0x00000080 R13 = 0xffffffff R14 = 0xffffffff R15 =
0xffffffff
R16 = 0xffffffff R17 = 0xffffffff R18 = 0xffffffff R19 =
0xffffffff
R20 = 0xffffffff R21 = 0xffffffff R22 = 0xffffffff R23 =
0xffffffff
R24 = 0xffffffff R25 = 0xffffffff R26 = 0xffffffff R27 =
0xffffffff 
						

							 
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Appendix B      ROM Monitor
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R28 = 0xffffffff R29 = 0xffffffff R30 = 0xffffffff R31 =
0xffffffff
frame—displays an individual stack frame.
sysret—displays return information from the last booted system image. This 
information includes the reason for terminating the image, a stack dump of 
up to eight frames, and, if an exception is involved, the address where the 
exception occurred; for example: 
rommon 8> sysret
System Return Info:
count: 19, reason: user break
pc:0x801111b0, error address: 0x801111b0
Stack Trace:
FP = 0x80005ea8 PC = 0x801111b0
FP = 0x80005eb4 PC = 0x80113694
FP = 0x80005f74 PC = 0x8010eb44
FP = 0x80005f9c PC = 0x80008118
FP = 0x80005fac PC = 0x80008064
FP = 0x80005fc4 PC = 0xfff03d70
FP = 0x80005ffc PC = 0x00000000
FP = 0x00000000 PC = 0x00000000
meminfo—displays size in bytes, starting address, available range of main 
memory, the starting point and size of packet memory, and size of nonvolatile 
random-access memory (NVRAM); for example:
rommon 9> meminfo
Main memory size: 40 MB
Available main memory starts at 0x10000, size 40896KB
IO (packet) memory size: 5 percent of main memory. 
NVRAM size:32KB
Exiting the ROM Monitor
You must set the configuration register to a value from 0x2 to 0xF for the router 
to boot a Cisco IOS image from Flash memory upon startup or reloading. 
The following example shows how to reset the configuration register and cause 
the router to boot a Cisco IOS image stored in Flash memory:
rommon 1 > confreg 0x2 
						

							 
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rommon 2 >boot
The router will boot the Cisco IOS image in Flash memory. The configuration 
register will change to 0x2101 the next time the router is reset or power cycled. 
						

							 
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APPENDIXC
Common Port Assignments
Ta b l e C - 1 lists currently assigned Transmission Control Protocol (TCP) port 
numbers. To the extent possible, the User Datagram Protocol (UDP) uses the 
same numbers.
Table C-1 Currently Assigned TCP and UDP Port Numbers
Port Keyword Description
0–Reserved
1–4–Unassigned
5 RJE Remote job entry
7ECHO Echo
9 DISCARD Discard
11 USERS Active users
13 DAYTIME Daytime
15 NETSTAT Who is up or NETSTAT
17 QUOTE Quote of the day
19 CHARGEN Character generator
20 FTP-DATA File Transfer Protocol (data)
21 FTP File Transfer Protocol
23 TELNET Terminal connection
25 SMTP Simple Mail Transport Protocol 
						

							 
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37 TIME Time
39 RLP Resource Location Protocol
42 NAMESERVER Host Name Server
43 NICNAME Who is
49 LOGIN Login Host Protocol 
53 DOMAIN Domain Name Server
67 BOOTPS Bootstrap Protocol Server
68 BOOTPC Bootstrap Protocol Client
69 TFTP Trivial File Transfer Protocol
75–Any private dial-out service
77–Any private RJE service
79 FINGER Finger
95 SUPDUP SUPDUP Protocol
101 HOST NAME NIC host name server
102 ISO-TSAP ISO-Transport Service Access Point
 
(
TSAP)
103 X400 X400
104 X400-SND X400-SND
111 SUNRPC SUN Remote Procedure Call 
113 AUTH Authentication Service
117 UUCP-PATH UNIX-to-UNIX Copy Protocol 
(UUCP) Path Service
119 NNTP Usenet Network News Transfer 
Protocol
123 NTP Network Time Protocol
126 SNMP Simple Network Management 
Protocol
137 NETBIOS-NS NETBIOS name service
Table C-1 Currently Assigned TCP and UDP Port Numbers (continued)
Port Keyword Description 
						

							 
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Appendix C      Common Port Assignments
138 NETBIOS-DGM NETBIOS datagram service
139 NETBIOS-SSN NETBIOS session service
161 SNMP Simple Network Management 
Protocol
162 SNMP-TRAP Simple Network Management 
Protocol traps
512 rexec UNIX rexec (control)
513 TCP—rlogin
UDP—rwhoTCP—UNIX rlogin
UDP—UNIX broadcast name 
service
514 TCP—rsh
UDP—syslogTCP—UNIX rsh and log
515 Printer UNIX line printer remote spooling
520 RIP Routing Information Protocol 
525 Timed Time server 
Table C-1 Currently Assigned TCP and UDP Port Numbers (continued)
Port Keyword Description 
						

							 
Appendix C      Common Port Assignments
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