1. Turn router off, hold reset, turn it on… or something similar, depending on the model (read the manual!)
2. atftp –trace –option “timeout 1” –option “mode octet” –put
–local-file ‘/images/openwrt-wrt54g-2.4-squashfs-7.09.bin’ 192.168.1.1
3. it is a question of the timing. Sometimes I had to repeat this several times.