Upgrade cisco router with public interface

[Fernandes]

A remote branch office has a router and I only have access to the outside interface. I can connect with public ip. How can I upgrade? what are your suggestions?

[Leo Laohoo]

Is the router remotely accessible or not?

[Fernandes]

Yes, I can access it via ssh

[Leo Laohoo]

What is the model of the router?

[Fernandes]

cisco C1111-4P

[Leo Laohoo]

Please read the Release Notes very carefully. 

Cisco ISR & ASR 1k Routers: IOS-XE/Firmware Upgrade (Install Mode)

[Fernandes]

Thank you for your help, but unfortunately this article does not provide information on how to send IOS to router with public interface.

[Leo Laohoo]

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@Fernandes wrote:

Thank you for your help, but unfortunately this article does not provide information on how to send IOS to router with public interface.

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From the router, enter the command (enable):  copy tftp://<TFTP_IP_ADDRESS>/filename.bin bootflash:".

[Fernandes]

Thank you for your help but I couldn't find any tftp server in public. I found public ftp on a site, configured DNS on the router and then uploaded it to the router.