I'm working on a Cisco 2851 router which has a flash disk in the front panel. I don't know how to upgrade an ios image using this flash disk. is it the same as using TFTP server? I know how to do it with TFTP server.
Working with the flash disk on the 2851 is essentially like working with normal flash on other routers. The same commands (such as copy tftp flash) work here the same way that you are used to.