Try follow steps:
- Download factory linksys firmware, rename to code.bin & copy to same tftp folder.
- Set your pc static ip is 192.168.1.10
- Connect pc to a switch by ethernet cable, connect switch to router lan port by another ethernet cable.
- Run tftp-client program example tftpd32 by Jounin, on tftp client tab: host 192.168.1.1 port 69, local file -> browse to code.bin file & click to Put.
- Power on router, it should flash.