Oh the danger of a public password for your wi-fi

[reggiep]

Yesterday afternoon, just before home time a few students couldn't log on to some laptops with wi-fi. They were getting a 169 IP address. I quickly gave up working it out as I had places to be.

This morning I came back in and looked at our DHCP and we had run out of addresses!

It then struck me that just before Christmas we had an iPad trolley trial and I had created a new WLAN just for the iPads that was locked down to mac address, but during one science lesson at the beginning of the trial a few ipads didn't take the profile so did not have the password for wi-fi. I wrote it on the board for the lesson and thought no more of it.

Anyway jumping back to today I had over 100 students phones and ipods connecting to it!

Keep in mind that although they were connecting to it they were not getting on to the wi-fi as it was locked down to mac address!

 

So anyway back to normal business now.

[reggiep]

I claimed back a total of 110 addresses in the end!

[Pyroman]

If it was MAC address restriced how was DHCP giving them addresses?

[reggiep]

It's a question I have been asking myself!

[zag]

If you use Windows 2008 R2 then just set up MAC address filtering on your DHCP server.

 

You can add all current devices with one click to the allow list.

 

Works really well here especially with BYOD becoming more popular.

 

We used to have exactly the same issues with the wireless password leaking and running out of DHCP addresses.

[cpjitservices]

They wernt getting an address though were they ? - hence the 169. address. ? Isnt this just a reserved address for if a machine cant get an IP from A DHCP server ?

[abillybob]

@cpjitservices Bang On. If the address started with 169 they wouldn't have been able to access your network or the internet via your wifi any how so it seems to me as if it's working as it should!