Use "/etc/init.d/network reload" instead of "/etc/init.d/network restart". The restart action will tear down the entire network, destroy all virtual interfaces (vlan interfaces, bridges, ...) and recreate them from scratch using other dynamically assigned interface indexes.
The reload action on the other hand will try to only apply the minimum amount of required changes without disrupting other network state. For example the change of an IP address or the addition of another interface should not affect the existing network interface topology.