A string of octets containing one bit per VLAN
for VLANS with 'VlanIndex' values of 0 through 1023.
The first octet corresponds to VLANs with 'VlanIndex'
values of 0 through 7, the second octet to VLANs 8
through 15, etc. The most significant bit of each octet
corresponds to the lowest 'VlanIndex' value in that
octet.
When a bit is set to '1', it means the
corresponding tagged VLAN as active for this user.