The Cisco “reload” command is used on almost all IOS Cisco networking devices (routers, switches etc) to restart (or reboot) the appliance.
This command might seem very basic but it has some interesting practical applications that we will see later in this article.
Basic Command Usage
As we have said above, the basic usage of this command is to reload the IOS operating system of the router or switch. Its the same as rebooting a computer.
If the current running configuration is modified and not saved to flash, the device prompts you to save the configuration.
The following example shows how to immediately reload a Cisco device:
CiscoRouter# reload
Another useful trick to know is to verify first the stored IOS image on the device before reloading:
CiscoRouter# reload /verify
The above will first perform a signature verification and file integrity check on the stored bootflash image file before reloading the appliance. After the verification is done the system will ask you again if you want to reboot the device.
CiscoRouter# reload [text specifying the reason]
e.g CiscoRouter# reload testing of Access Control List
The above specifies the reason of reloading the system.
How to schedule a reload
Now this is the useful practical application of the reload command we have mentioned at the beginning.
By scheduling a reload at some specified time in the future allows the administrator to make critical changes to the configuration that might drop connectivity or have some other traffic implications.
If something unexpected happens after the configuration change, the device will reboot by itself in let’s say 2 minutes from now thus restoring the previous state of the network.
Let’s see how reload scheduling works:
There are two keywords that you can specify for reload scheduling:
reload at [specific date and time]
reload in [minutes]
Examples:
CiscoRouter# reload at 14:00
The above will reload the router at 2:00pm in the current date.
CiscoRouter# reload at 14:00 jan 10
The above will reload the router at 2:00pm on January 10.
Both of the above commands assume that you have correct clock settings configured on the device (NTP or manual system clock setting).
CiscoRouter# reload in 2
The above will reload the router in 2 minutes from now. Very useful as we will see in the special case below.
CiscoRouter# show reload
The above shows the current state of the reload command. If you have scheduled a reload operation after some time from now, the above command will show the exact time when the device will reboot.
CiscoRouter# reload cancel
The above will abort any scheduled reload operation.
Practical Use Case of Scheduling a Reload
Assume you are connected remotely to a router on the other side of the world and you are configuring some “dangerous” commands such as changing an IP address on an interface, applying Access Control Lists, making changes to a dynamic routing protocol etc.
The above configuration modifications can kill your connection to the appliance, interrupt traffic communication, lock you out of the device etc. By scheduling a reload will provide a “safety net” for the above unexpected situations.
Let’s see what to do if you are working remotely on a Cisco device:
Step 1:
First save the current working configuration before making any changes:
CiscoRouter# wr mem
Step 2:
Schedule a reload in 5-10 minutes (depending on how much time you need).
CiscoRouter# reload in 5
Step 3:
Perform the required configuration changes on the Cisco device (e.g IP change, ACL changes etc).
Step 4:
If the configuration changes in Step 3 are successful (i.e they didn’t kick you out of the device or blocked any traffic etc), then cancel the reload command and save the newly updated configuration.
CiscoRouter# reload cancel
CiscoRouter# wr mem
Now, if for any reason you made a mistake or the new configuration causes a network problem, the router will reboot itself in 5 minutes thus returning to its previous working configuration before the changes.