A string of octets containing one bit per VLAN
for VLANS with 'VlanIndex' values of 1024 through 2047.
The first octet corresponds to VLANs with 'VlanIndex'
values of 1024 through 1031, the second octet to VLANs
1032 through 1039, 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.