由于不小心使用了命令erase flash或升级失败后或在开启（某些型号）cisco路由器的电源开关后30秒内按下ctrl+break键，中断路由器的正常启动，路由器都会进入rom监视模式，即 rommon 1>，在这种情形下，对路由器的ios进行升级，情况要稍微复杂一点。在rommon 1>状态下，可键？请求帮助。（1为命令行序号，每执行1条命令自动加1）
quote：rommon 1 > ？
alias set and display aliases command
boot boot up an external process
break set/show/clear the breakpoint
confreg configuration register utility
cont continue executing a downloaded image
context display the context of a loaded image
cookie display contents of cookie prom in hex
dev list the device table
dir list files in file system
dis display instruction stream
dnld serial download a program module
frame print out a selected stack frame
help monitor builtin command help
history monitor command history
meminfo main memory information
repeat repeat a monitor command
reset system reset
set display the monitor variables
stack produce a stack trace
sync write monitor environment to nvram
sysret print out info from last system return
tftpdnld tftp image download