Today i had to shutdown one virtual interface, but when i was trying to start it again i faced some problem:
ifconfig eth0:1 up
SIOCSIFFLAGS: Cannot assign requested address
At first i thought it was some kinda bug related to my system, but than reading some post and manuals i realised that ifconfig is not a perfect network configuration tools and sometimes it behaves inadequately in network environments especially when you are managing virtual interfaces. Instead of using ifconfig while managing virtual interfaces it is way better to use iproute instead. Iproute is usually shipped in a package called iproute or iproute2 and includes several tools most important ones are ip and tc. ip controls IPv4 and IPv6 configuration and tc is for traffic control.