Unless you have resolved your router problem, read below, curtesy of cisco web-page.
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......a checksum failure indicates that the file has not been properly copied into the memory and you need to copy it again.
First, verify that the file you copied to the TFTP server is the same size as the original file. (Be aware that the size is listed in bytes in the router and is sometimes listed in kilobytes in TFTP servers.) If the network is very busy, you may also see this behavior; try the copy again when the
network is not so loaded, or establish a direct Ethernet connection between the TFTP server and the router to download the file.
I hope this helps.
Emil.
