A string of octets containing one bit per VLAN
for VLANS with 'VlanIndex' values of 2048 through 3071.
The first octet corresponds to VLANs with 'VlanIndex'
values of 2048 through 2055, the second octet to VLANs
2056 through 2063, 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 indicates the
corresponding tagged VLAN as active for this user.