At the end we have realized that his switch was configured for such behavior.
Force10 FTOS supports two reload types
- reload-type jump-start
- reload-type normal-reload
If jump-start mode is used then configuration is cleared after each reload. This reload type is useful for product demonstrations, technology introductions or proof of concepts. But it can be very frustrated for someone who want to use switch in production.
Solution is very simple. You just need to change reload type by single command "reload-type normal-reload"
Hope this saves time to someone.