When to use copy start run

So, I have a quick question for an IOS command.

When would you use "copy start run?"

If "copy run start" writes into NVRAM for next-boot, what does the first one do?

Thanks.

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Hondabuff

Thats if you used a TFTP server to import your saved config to the startup location. To make it active you would do the copy start run and enable any down interface. I have used this on a switch and made a backup of the startup config incase of failure.

networker050184

It writes from NVRAM to the current running config. The thing to keep in mind is that this is a merge operation.

Futura

If you mess up your router and you change the config register to not load the config when it boots then you can copy the start to run and reset the passwords etc.

iamme4eva

My advice would be...don't.

As networker said, it's a merge operation, so you won't necessarily get what you expected. If you TFTP a startup config into your router, you might be surprised when you copy start run and everything doesn't quite work as expected because you still have residual config from your previous running config left.

Best option after TFTP'ing a startup config in is to do a reload.

bushwack

I would like to ask,

The result of the command 'copy start run' and reloading/rebooting the router/switch would be the same? regardless of whatever commands the running config had?

iamme4eva

bushwack, not quite.

As network said earlier, it's a merge.

copy start run would be like adding your startup config to your running config, without overwriting things that aren't mentioned in the start config. example:

(simplified for ease) current running config:

interface fastethernet0/0[INDENT]duplex half
ip address 10.0.0.1 255.255.255.0
no shutdown[/INDENT]

startup config:

interface fastethernet 0/0[INDENT]shutdown[/INDENT]

if you did a copy start run here, the running config would look like this:

interface fastethernet0/0 [INDENT]duplex half
ip address 10.0.0.1 255.255.255.0
shutdown[/INDENT]

It doesn't erase the running config first, it simply merges.

bushwack

I didn't get the merge thing 'till I saw your sample. That cleared me, thanks a lot!

networker050184

If you want to completely replace the config using the config replace command is a much better option.