The D-Link FTP Server maintains an active directory of firmware for Hardware Revisions B1 and C1, including the DNS-323_C1_FW_v1.10 files.
If you want, I can draft a shorter how-to checklist for non-technical users or produce terminal commands for the TFTP/serial recovery path. dns323 firmware 111 download fix
If the device fails to update or you cannot find "1.11," follow these fixes: D-Link DNS-323 Firmware Update Issues - JustAnswer The D-Link FTP Server maintains an active directory