Is it somehow possible via software to disable NIC in such manner, that even "link protocol" in Cisco switch will not come up? I connected laptop eth0 port to switch port and console cable to switch management port as well. If I do "ifconfig eth0 down" or "ifdown eth0", the link protocol still stays up. Even after "modprobe -r e1000e" autonegotiation between NIC and switch port takes place and link protocol comes up As far as I know, there are no possibilities to disable NIC using the ethtool or mii-tool. Any suggestions? Or is it possible at all?

Which distro are you running?