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detect presence of users by wifi possible?

detect presence of users by wifi possible?

(OP)
Hi All,

I been pondering for a while a method by which to detect users at a location. We have 3 offices and users usually roam from one office to the other. I been thinking about a solution that would allow me to detect their presence at either location. I know there is apps out there that do this( using gps) but those require a budget which I don't have.

My users all have iPhones and when the arrive at each location their phone immediately jumps onto the wifi at the location. I been thinking about essentially using the dhcp even log generated when they jump on wifi and attaching a task to it. I think I could identify user by mac address of device or device name. Its all theory at this point I haven't tried, but hoping some one can shed some of their experience on the possibilities of this.

My question is simply besides the log entry on the dhcp generated when they get an IP - is there a way to ping that device at intervals to know if its still around? I mean someone could show up at an office and leave 15 minutes later so I need to be able to tell when their device is no longer on premises. ideas? insights?

Thank you

RE: detect presence of users by wifi possible?

Is your DHCP server Microsoft DHCP for the Wireless or does it use DHCP on a Wireless Access Point?

You can query DHCP current leases, would likely want them to expire very quickly to tell who is active, I doubt that ICMP traffic is enabled on any phone to allow a ping response back. So your best bet would be to expire DHCP leases quickly and see who renews and does not.

Once you get a list of active MAC addresses, you could use a dictionary object to translate that to user names and could then export the list to an HTML page that would allow easy lookup.

I hope that helps.

Regards,

Mark

Check out my scripting solutions at http://www.thespidersparlor.com/vbscript

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RE: detect presence of users by wifi possible?

(OP)
@markdmac

Thank you for your reply. I went ahead and implemented this according to your insights and it seems to be working decently good. Is there any drawbacks/implications that you might be aware of expiring leases quickly? Currently I have it set at 10 mins.

Thank you,
Rodrigo

RE: detect presence of users by wifi possible?

The disadvantage of the quick expiration is just that the devices will need to frequently negotiate, so every five minutes (half time of your lease) they contact DHCP to say they want to renew. They then get extended. You may want to extend to 30 minutes. That way live devices only need to contact DHCP every 15 minutes and removed devices will lose their lease at 30 minutes.

If my suggestion was helpful, please consider adding a star to the post so others will know it was helpful.

I hope that helps.

Regards,

Mark

No trees were harmed in posting this message, however a significant number of electrons were terribly inconvenienced.

Check out my scripting solutions at http://www.thespidersparlor.com/vbscript

Work SMARTER not HARDER.

RE: detect presence of users by wifi possible?

(OP)
@markdmac

Yes. I did look up the dhcp process. 15 minutes made sense as that would ensure the accuracy of the information is within +-15 minutes. I was thinking even shorter so make accuracy even better, but my concern was network traffic caused by renewal of the IP, or request for an IP. Is this traffic broadcasted or is it directly sent to dhcp server?

Again, thanks for the input.
Rodrigo

RE: detect presence of users by wifi possible?

It is broadcast initially, but then the device knows the address of the DHCP server and will renew directly to it. Here is an older article that talks about DHCP that may help fill in some gaps, the technology has really not changed much over the years. DHCP

I hope that helps.

Regards,

Mark

No trees were harmed in posting this message, however a significant number of electrons were terribly inconvenienced.

Check out my scripting solutions at http://www.thespidersparlor.com/vbscript

Work SMARTER not HARDER.

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