The -c option in Xmodem file transfers is used to enable CRC (Cyclic Redundancy Check) for enhanced error checking. Here's why it's the correct answer:
Error Detection: CRC is a more robust error detection mechanism compared to the standard checksum method used in Xmodem. It provides greater reliability in identifying file corruption during the transfer.
Flash Memory: Since flash memory on a Cisco router or switch stores critical data like configuration files or the IOS image, ensuring the integrity of transferred files is crucial.
Why other options are incorrect:
-e, -r, -x: These are not standard Xmodem options for error checking purposes. While some implementations may have custom flags, they are not universally applicable.
Important Note: Xmodem is a legacy protocol that is often replaced by more reliable options like TFTP in modern Cisco devices. However, understanding Xmodem options is still relevant for certain cases or older equipment.
Reference:
Xmodem overview: https://en.wikipedia.org/wiki/XMODEM
Cyclic Redundancy Check (CRC): https://en.wikipedia.org/wiki/Cyclic_redundancy_check