Hi, The documentation for SIOCGIFFLAGS/SIOCSIFFLAGS in netdevice.7 lists IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO, but those can't be set in ifr_flags as it is only a short and the flags start at 1<<16. See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=746e6ad23cd6fec2edce056e014a0eabeffa838c Thanks, // Erik