Infrastructure mode and ad hoc mode at the same time?
In setting up a wireless network with a wireless broadband router, do you
need to disconnect the firewalls in order for computers on the same SSID to be able to access each
other? Can you run two different wireless networks, one that allows the other laptops to access the
Internet, and an ad hoc network for a WLAN?
Most wireless broadband routers do not filter traffic exchanged between stations on the same
wired or wireless LAN. Instead, firewall filters are applied to traffic flowing between the LAN and
the WAN (Internet). Therefore, two stations using the same SSID to access the same infrastructure
mode WLAN can usually communicate with each other by relaying LAN frames through the wireless
Some APs do support multiple SSIDs by using a single radio tuned to one channel. However, if a
device only has one radio, it cannot operate in both infrastructure mode and ad hoc mode at the
same time. Therefore, your laptop can either connect to SSID#1 in infrastructure mode to reach the
Internet through your wireless router, OR it can connect to SSID#2 in ad hoc mode to directly reach
another station, but it cannot do both simultaneously unless it has two wireless PC cards.
This was first published in March 2004