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public ip addresses

Posted on 2008-10-04
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The Orange mobile NAT structure does not map the internal ports to public ports. For example a private IP 10.85.32.56 and port 5000 may be mapped to a public IP of 85.234.32.14 and the same port 5000 i.e. the port is not mapped.

But, what happens if two or more devices open up the local port 5000 within the same network? Can this be an issue or do every 3G device have a seperate public IP address with Orange for example?

When I run IPconfig in command prompt I get the subnet 255.255.255.255.....which I presume means that I'm the only device on that subnet and that every device has a unique public IP addresses. If so then how can Orange hold so many public IP addresses?????
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Question by:smotbd
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Darr247 earned 1500 total points
ID: 22642612
> But, what happens if two or more devices open up the local port 5000 within the same network?

They're probably opening a different socket (IP+Port)... got any real world examples?


> Can this be an issue or do every 3G device have a seperate public IP address with Orange for example?

They SHOULD each be given separate IPs from Orange's pool... same as ISPs used to do with dialup modems, in fact it's exactly the same since 2G and 3G devices (and probably mobile 4G devices soon to come) are technically dialup modems. They just all dial numbers like #777 or *98.


> If so then how can Orange hold so many public IP addresses?????

It has a pool of IPs and doles them out as its customers connect, returning them to the pool when they disconnect.

I'm not seeing where your confusion lies in the situation described, since you seem to have a good grasp of it.
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by:smotbd
ID: 22642879
Well if they are all given an unique public IP address then there will not be an issue with two device opening the same port value....I believe that Orange use unique public IP addresses to each mobile devices connected as you said. This explains why I get a subnet of 255.255.255.255. BUT why do this? Why is this common with dial up networks?

Also: What if lots of people in the UK connect to Orange the same time? - how many people can be connected - surely Orange cannot accomodate for a huge demand as there are only so much public IP addresses in their pool.

Note however: Vodafone on the do not give a unique IP address to all mobile device connected. I.e. two devices might have the public IP address of 212.183.134.209. In fact they seem to only have a handfull of IP address - i have tested this by connecting and disconnecting 50 times and checking my ip address each time. Thus not all dial-up devices have a  unique IP address?????? However, vodafone do map the ports unlike Orange so again two device could open port 5000 locally and be mapped to the same IP address but the ports will be mapped differently.
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by:Darr247
ID: 22643127
> This explains why I get a subnet of 255.255.255.255. BUT why do this? Why is this common with dial up networks?

It keeps you from accessing other hosts in that subnet (and vice-versa). Note that the Gateway doesn't count... you're not really 'accessing' it, and the listed Gateway doesn't need to be in the same subnet anyway.


> i have tested this by connecting and disconnecting 50 times

If the device doesn't explicitly release the IP address, vodaphone's DHCP server could have just been giving it the same address it already had assigned it because the lease hadn't expired yet.


> Thus not all dial-up devices have a  unique IP address?????? However, vodafone do map the ports unlike Orange so again
> two device could open port 5000 locally and be mapped to the same IP address but the ports will be mapped differently.

That's odd, but using different ports would still result in different socket addresses.
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by:smotbd
ID: 22656025
>It keeps you from accessing other hosts in that subnet (and vice-versa). Note that the Gateway doesn't count... you're not really 'accessing' it, and the listed Gateway doesn't need to be in the same subnet anyway.

But- why stop devices from accessing other hosts in the same subnet? Why so dail-up networks all employ this?
Besides I can communicate between two mobile devices on the Orange mobile network for example via their private IP addresses so doesn't that contradict what you suggest?
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by:Darr247
ID: 22656707
> But- why stop devices from accessing other hosts in the same subnet? Why so dail-up networks all employ this?


Some people don't WANT others accessing whatever devices are connected via the IP they are assigned. If they do want to allow that, they can run a dynamic DNS client (http://www.dyndns.com/services/dns/dyndns/howto.html) from a computer tethered to the phone (or if the phone's tethered to a 3G router like Cradlepoint, Kyocera, et al, makes... it's been a while since I've seen a router without DDNS support).
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