geocoding IP addresses

I am trying to figure out how accurate the MaxMind GEOIP service really is.

I am on dialup, but somehow it seems to guess my actual location with remarkable precision. My ISP is not located anywhere near here (it is in Brisbane I think), but there is a national toll free dialup

Here is the tracert

Tracing route to []
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  VIRGO []
  2   121 ms   124 ms   124 ms [
  3   122 ms   124 ms   124 ms [203.220.2
  4   122 ms   124 ms   124 ms [203.1
  5   122 ms   124 ms   124 ms [203
  6   122 ms   125 ms   124 ms [203
  7   122 ms   124 ms   124 ms []
  8   122 ms   140 ms   124 ms
  9   138 ms   140 ms   124 ms []

 10   138 ms   155 ms   156 ms [150.101.180
 11     *        *        *     Request timed out.
 12   152 ms   140 ms   156 ms []
 13   139 ms   140 ms   140 ms []

Trace complete.

and this is the o/p from the demo at maxmind

Your IP Address
Countries       Australia
Region       02 (New South Wales)
US Area Code       
US Metro Code       
Global Cities       Ilford
Latitude/Longitude       -32.9667/149.8667
ISP       COMindico Australia
Organization       COMindico Australia
Netspeed       Dialup
Domain Name

The suburb guess is remarkably close.

Note that Maxmind guesses my IP as which is not on the tracert listing above.

Now, my understanding of dialup ISPs is that they randomly issue you an IP address from "their" block. I guess it is kown somewhere what blocks are assigned to what ISP's, but that would only get you to where the ISP is located. So, how can they get close to me when I am many hundreds of miles from my ISP??

Also, how would this work if someone is on broadband/cable? Say I was sitting in Los Angeles .. could it tell whether I was in Beverly Hills or in La Brea?
Who is Participating?
Well, where you are, I don't really know if it differs, but I can speak for North America. Most broadband providers do not give you a "fixed" address (called "static ip address") unless you pay extra for it. And the ip address for that will follow the same allocation conventions as the dynamic addresses. The addresses may be broken down by region, by state, even by city suburb. It depends on the subscriber density. The subscribers in a certain area will all connect through the same "access concentrator" that basically is the connection point between the user and the providers network. Anywhere from 2 to 4000 or so end users in a specific city area will have a common connection point to the internet. This is the "edge router" that assigns the actual IP address to the user. So to manage the entire network, the ISP will assign a "pool" of addresses for each edge-router to hand out. The overall IP block assigned to the ISP doesn't get tied to a region, but the ISP will assign each region a pool to use. This makes network routing tables easier for the equipment to self-manage, reducing latency, blah blah blah. So it's basically the same for broadband as it is for dial-up.

What it comes down to is the more dense the population in a given area, the more accurate the service is likely to be. With static IP addresses, you can get a GPS level of accuracy on it, as long as someone provides the data to the service. I have traced some addresses to a specific office on a particular floor of a building in a major US city, because someone who worked there provided the exact coordinates of their own router. That said, I live on a rural route, and it may be a 20 minute drive to the place that gets the next ip address in the same dynamic pool I draw from.

So, how granular can this get? Well, a zip code can cover a small, densely populated area, or it can cover a fairly large area. Beverly Hills to La Brea is about a 40 mile drive, so, yes, this is possible. There are always fudge-factors: some ISPs use proxy servers for instance, so the IP the service looks at may be far away from you. Still, the hit-rate is pretty good.
Many ISPs divide the address pools by geographic region, mostly for managment purposes, so the address you get is often tied to the region you dialed into, or even where you dialed from. Those smaller blocks can be tracked, and some ISPs contribute to the tracking, by third parties. MaxMind is one of those. They track what ip addresses are where. Some services allow users to contribute thier own location to the database, which adds to the accuracy (NeoTrace Pro was one of those, now part of McAfee Visual Trace). So they can be very accurate, as long as the database is regularly updated. The commercial services like MaxMind tend to be fairly accurate.

There are ways to fool it, however. Proxy servers, long-distance calls, etc. If you made the long distance call to connect to a dial-up ISP in Beverly Hills, MaxMind might think you were there.
Mutley2003Author Commented:
ok, bear with me a little, please

1. does the situation with broadband differ? If I understand it correctly, with broadband you get a fixed IP address? Is that so, and if so, does the address get tied by the broadband provider to some small geographic region? .,. for example, are all the broadband customers of MegaTelco in Watts going to have IP's in a block more or less specific to the suburb?

2. I am still not sure how granular this really can get. I am not in the US, but MaxMind says it provides zipcodes. So, do these really distinguish between say, Beverley Hills and LaBrea - or is accuracy at that level really suspect?


Mutley2003Author Commented:
great, thanks for the full explanation
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