how to calcuate the checksum of Zyxel NDMS V2.0 firmware.

[calliou]

Hi All,

I would like to ask how to calcuate the checksum of Zyxel NDMS V2.0 firmware. I try to unpack and pack the firmware but something wrong by use the web interface to upgrade new-firmware.bin. I have download the firmware KEENETIC-V2.00[BFW.3]B11.bin from Zyxel.ru. I guess last 4 bytes are checksum bytes and a1 b3 ea ec is actual checksum value and I try to use cksum it said that checksum value is not correct.
Anyone knows how the checksum calculation logic for this kind (Zyxel NDMS V2.0) of firmware ?
Many thanks for your help.

[root@localhost image_parts]# hexdump -C /opt/zyxel/KEENETIC-V2.00[BFW.3]B11.bin |tail

005536e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00560000  5a 4e 42 47 15 42 00 00  5a 79 58 45 4c 20 63 75  |ZNBG.B..ZyXEL cu|
00560010  73 74 6f 6d 00 00 00 00  00 00 00 00 00 00 00 00  |stom............|
00560020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00560030  00 00 00 00 00 00 00 00  a1 b3 ea ec              |............|
0056003c