Showing posts with the label SSID

Microsoft NPS as a RADIUS Server for WiFi Networks: SSID Filtering

The Microsoft Network Policy Server (NPS) is often used as a  RADIUS server for WiFi networks. It can provide authentication and authorization services for devices and users on a wireless network in a Windows Active Directory environment. In this article we look at how we can use NPS to provide authentication for WiFi users across a number of SSIDs. We have previously discussed how to authenticate groups of users using the same SSID and then assign them to a VLAN that is appropriate to their security authorization. However, there may still be instances where two or more SSIDs are in-use on a wireless network and we would like to base policy decisions on the SSID that the authentication request is being generated from. As an example, if we consider a school, perhaps we would like students to only be able to authenticate if they connected to the SSID: "Student_Net". Similarly,  staff should only be able to connect using the SSID: "Staff_Net". This would

How Much Air-Time Do Beacons Actually Burn?

It’s a well known rule of thumb when designing WiFi networks that you need to try to keep the number of SSIDs broadcast by your wireless network  down to a ‘reasonable’ number. In this article, I take a look at how much of an issue SSIDs (and their beacons) are in consuming valuable wireless air-time. Generally, it’s recommended to keep the number of SSIDs below around 5 (ish). The reason for keeping the number of SSIDs to a minimum is that each SSID is advertised using a type of management frame called a ‘beacon’.  Beacons are generally sent 10 times per second for each SSID on the wireless network. Therefore, if you have 10 SSIDs, they will each be advertised 10 times per second, giving us 100 beacons per second. Air-time is a finite resource – there is only so much data that can be transferred across the air over a period of one second. If a large chunk of air-time is being consumed by SSID beacons, then that doesn’t leave a whole lot of time remaining for actual user d

Fast SSID Change - Out Of The Shadows

There are many configuration settings on a piece of networking kit that are just 'there'. They sit there year after year just minding their own business being a quiet little chunk of configuration sitting in their default state not doing anyone any particular harm. Then, occaisionally, you come across some obscure case that causes you to actually pay attention to what exactly that particular setting is 'bringing to the party'. One particular instance I came across recently is the 'Fast SSID Change' setting on a Cisco WLC. From memory, it's been sat there for quite a while on many of the controllers I've installed, sitting dutifully in its default state of 'Disabled'. I've never really paid it much attention as it doesn't (on the face of it) seem to cause anyone any particular problems. However, I recently ran in to a situation where a customer had some Apple iPads that he wanted to connect to an SSID that was mapped to an internal