The warm reload feature of the Cisco IOS was offered in IOS version 12.3(2)T.

How to perform a warm upgrade in the Cisco IOS

Use the reload warm file command, like this:

Router# reload warm file tftp://1.1.1.1/c2800nm-advipservicesk9-mz.124-15.T5.bin

This command actually has a number of options such as scheduling and creating a comment:

reload [/verify | /noverify] [warm [file url]] [in [hh:]mm | at hh:mm [month day | day month

The job of the warm reload feature is to allow you to reload your routers without having to read the IOS image from flash.

How do you use warm reload in the Cisco IOS?

The job of the warm reload feature is to allow you to reload your routers without having to read the IOS image from flash.

You can configure the warm reboot functionality with the warm reboot global command, like this:

Router(config)# warm-reboot 10 uptime 10

This enables the router to reboot a maximum number of 10 times using the warm reboot function and ensures that the router will sit for no more than 10 minutes after an attempted warm reload that doesn’t result in a successful boot. Next, you must do one clean, cold reload of the router. After that, you can use the reload warm command to quickly reboot your router.

You can also use show warm-reboot to find the statistics concerning how many warm reloads have happened and how much space is taken up by warm reload storage.

1. power off and back on the device
2. hold down control and hit BREAK (may have to do this a few times)
3. Once you are at the rommon> prompt, type confreg.
4. Say “n” to all options except this one:
enable “ignore system config info”? y/n [n]: y
5. Say “n” to all other options
6. once back at the rommon prompt, type reset
7. the device will reboot
8. Once the device is booted, you will know that you are bypassing the config because you will be asked this question (say no):
Would you like to enter the initial configuration dialog? [yes/no]: no
9. Once booted, if you do a show version, you will see that your config register is 0×2142.
10. Now, you can either go to enable mode and do a show startup-config to see what the enable password is OR, if you have an enable secret password set, you can replace it by doing a copy start run, then going into global configuration and creating a new enable secret with enable secret cisco, then copy it back with copy run start.
11. Now, you want to change the config register back. In global configuration, type config-register 0×2102
12. save your configuration with wr or copy run start

Trivial File Transfer Protocol (TFTP) over the first LAN port using the ROMmon tftpdnld command.

All variable names are case sensitive. You can view the ROMmon environment variables by using the set command, as shown here:

rommon >
    Set IP_ADDRESS=172.18.16.76
    Set IP_SUBNET_MASK=255.255.255.192
    Set DEFAULT_GATEWAY=172.18.16.65
    Set TFTP_SERVER=172.18.16.2
    Set TFTP_FILE=quake/rel22_Jan_16/c2600-i-mz
rommon > tftpdnld