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When I try to connect to a free WiFi, my Xperia Android smartphone displays:

obtaining ip address

  • Why does it happen?
  • Which IP address is that?
  • Is it static or dynamic?
  • Does this IP address identify my smartphone?

Or does it identify the WiFi router and is its IP address common for different smartphones/laptops?

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migrated from superuser.com Jul 20 '11 at 0:29

This question came from our site for computer enthusiasts and power users.

    
If you're concerned about privacy, keep in mind that most free wifi is unsecured & unencrypted. –  Joe Internet Jul 20 '11 at 0:23
3  
Bad migration ... this is not Android-specific. –  Matthew Read Jul 20 '11 at 15:15
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3 Answers 3

When it says that, while connecting over wifi, it means that the machine is asking the local network for connection information. On a basic level it's already connected. But when it says that, it doesn't yet have an IP address and thus can't yet transfer TCP nor UDP traffic (probably some other types too, like ICMP).

So it's really trying to get assigned an IP address for use on the local network, which is something handled by a DHCP service (usually in the router).

This is not special to the device type, it's just something that's a part of networking.

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1  
so, is this ip address private?? (10.x.x.x; 192.168.x.x; 172.16.0.0 - 172.31.255.255) –  DrStrangeLove Jul 19 '11 at 22:15
    
The second one for sure. The first one, probably is. The range at the end, I don't know wtf that is. But if it's over wifi, then it's local to that network. I really doubt it's public to the internet from there-- Though there are ways of knowing the private IP, but you can't open connections to it without special provisions. –  The White Phoenix Jul 19 '11 at 22:19
    
See RFC 1918, section 3 (on page 4) for the official list of private IP address blocks (all the blocks mentioned in the first comment above are definitely reserved for private use): rfc1918.openrfc.org –  Randolf Richardson Jul 19 '11 at 22:24
    
@Randolf - thanks –  The White Phoenix Jul 19 '11 at 22:39
    
Being part of an RFC 1918 range ("private IP") does not mean that your data is secure. It just means that the IP address can't be directly routed from the Internet without some form of address translation and/or proxy server. –  TomG Jul 20 '11 at 2:23
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Why does it happen: When you connect to a DHCP enabled router, your device (notebook, smartphone etc) obtains an IP address in order to access internet via that router/server.

Which IP is that, static or dynamic: It's a dynamic internal IP address and is valid only within that network.

Does this IP address identify my smartphone: Yes, but only in that network and it's actually the MAC address of your network adapter that identifies your device, not your IP.

The same is true for the router. It may have a static or dynamic IP which is given by the ISP. If it's static then yes it identifies it, otherwise no. Your external IP (router's IP) is different from your internal IP. All of the devices connected to that router have the same external IP address.

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All of the devices connected to that router have the same external IP address. This is not necessarily the case, but if you're in a network where this isn't true, then you probably already know about it. –  Lie Ryan Jul 20 '11 at 3:35
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If your smartphone says "obtaining ip-address" it means it is searching for an IP address or connecting to an IP address. If you are trying to connect via Wi-Fi using the smartphone, it may be a static IP address or dynamic ip address. Your IP address won't identify the device, but the device has to obtain an IP address if you connect to the internet and the service provider will know about your device. Every device connected to the internet has its own IP address. Visit this site to check the internet IP address for your smartphone, iPad, PC or laptop.

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"Obtaining" always refers to a dynamic (DHCP) address. A static address you would need to configure manually, and then the device would not need to "obtain" it. "Connecting to an IP address" is something completely different again, as for "connecting to" the address must already be known. Plus, the "provider" has nothing to do with your WiFi :) –  Izzy Mar 28 '13 at 10:24
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