f.write('\t\t<VLAN_slave_of/>\n')
f.write('\t\t<VLAN_master_of>OpaqueRef:NULL</VLAN_master_of>\n')
f.write('\t\t<VLAN>-1</VLAN>\n')
f.write('\t\t<VLAN_slave_of/>\n')
f.write('\t\t<VLAN_master_of>OpaqueRef:NULL</VLAN_master_of>\n')
f.write('\t\t<VLAN>-1</VLAN>\n')