Draytek Vigor3200 Series User Manual page 78

Hide SSID
Long Preamble
Vigor3200 Series User's Guide
Check it to prevent from wireless sniffing and make it harder
for unauthorized clients or STAs to join your wireless LAN.
Depending on the wireless utility, the user may only see the
information except SSID or just cannot see any thing about
Vigor wireless router while site surveying. The system allows
you to set four sets of SSID for different usage. In default, the
first set of SSID will be enabled. You can hide it for your
necessity.
This option is to define the length of the sync field in an 802.11
packet. Most modern wireless network uses short preamble
with 56 bit sync field instead of long preamble with 128 bit
sync field. However, some original 11b wireless network
devices only support long preamble. Check it to use Long
Preamble if needed to communicate with this kind of devices.
68