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This question is in two parts.

Q1.

How does a mobile phone get an IP address over 3G? Like, would it get the same IP for a shortish period of time (Eg. 1 day, etc)? Because my phone is constantly going in and out of buildings and underground car parks, i'm jumping between cell hotspots/receiver towers, so would I be getting a new IP each and every time? I feel like this is back to the old modem days -> every time i 'ring in/jump onto the interwebs' I get allocated a new number.

Or does it have some mac address and the Telco's mobile phone DHCP server keeps reusing the last IP based on the mac, for a specific perioud of time (eg. TTL for an IP, like a normal DHCP which has an expiry setting for the allocated IP).

Q2.

If the previous answer is that mobile's keep getting different IP's, does this mess with google analytics and the unique visitor's value? So if i'm getting 5 IP's for a day on my mobile, would that mean i'm 5 unique visitor's for the website i'm tracking?

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2 Answers 2

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How does a mobile phone get an IP address over 3G?

I'm going to guess that this all depends on your provider. I'm with Optus in Australia and my IP changes fairly frequently, but I've never really looked into "why".

Does this mess with google analytics and the unique visitor's value

Unique Visitors is determined by a cookie. If you turn on HTTP Headers in your favourite FireFox plugin you should be able to see it being sent. It usually looks something like __utma=(long string). So movement of IPs should not affect this. Especially as you can also have thousands of users represented by one public IP it would not be fair to use the IP for tracking uniqueness.

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Q1: Most 3G mobile providers uses a DHCP pools of private addresses and a NATed Internet access (for IPv4, this is the most flexible way to control the address allocation and Internet flows). Some corporate solutions can offer a pool a public addresses.

Q2: Google Analytics does not rely entirely on the IP address to collect statistics. It also uses User-Agent, cookies, etc.

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I assumed that phones get their IPs from PPP not DHCP. Otherwise, as you say, google has ways of knowing. –  chris Dec 10 '09 at 10:10

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