Upgrading ASA or for that matter any device is really a very simple procedure, however sometimes due to some very simple yet difficult to diagnose issues the upgrade process can go for unexpectedly long
This documents hopes to identify some common issues which we encounter when performing upgrades
Copy TFTP flash fails midway through the image load
This happens usually when there is network congestion and packets get lost in between tftp server and asa, also remember tftp is an unreliable protocol which works on udp port 69
Resolution: Connect the tftp server direcly to asa or through a switch
tftp server ----------------switch-----------asa
Also try not to upload image over vpn tunnel using tftp
if the number of hops are more then it is suggested that you use ftp to upload files to flash
https://supportforums.cisco.com/docs/DOC-12658
