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Lumia can somehow access external ip from internal network

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  • 28-11-2015 11:04am
    #1
    oceanclub
    Registered Users Posts: 3,411 ✭✭✭


    I have a server running on my desktop on UPC, where unfortunately you can't access an external IP from the internal work. So, from my iPhone while on my home network, I can't connect to the external IP; i have to either go off the network onto 3G or use the internal IP of the desktop. That behaviour is annoying but as expected.

    However - an my wife's Lumia _can_. I've checked that she's definitely connected to the same network. Weirdly, if she's tries to connect via the external IP, that doesn't work but she can connect via the hostname I've set up for our external IP (from http://www.noip.com/).

    Is the Lumia doing some magic I'm unaware of (like, reverting to using 3G if it can't connect using wifi)?
    P.


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    #2
    ED E
    Registered Users Posts: 36,167 ✭✭✭✭ED E


    Weird that one client could and the other couldnt. Hairpin NAT is a function of the router not its clients.

    Grab a ping app on the lumia, ping the hostname and see if its somehow resolving it to a local address or the normal WAN. "Weirdly, if she's tries to connect via the external IP, that doesn't work but she can connect via the hostname" - This would point to the former. Then its just a question of what its DNS is doing.


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    #3
    oceanclub
    Registered Users Posts: 3,411 ✭✭✭oceanclub


    ED E wrote: »
    Weird that one client could and the other couldnt. Hairpin NAT is a function of the router not its clients.

    Grab a ping app on the lumia, ping the hostname and see if its somehow resolving it to a local address or the normal WAN. "Weirdly, if she's tries to connect via the external IP, that doesn't work but she can connect via the hostname" - This would point to the former. Then its just a question of what its DNS is doing.

    Thanks, I tried ping on the Lumia, and the hostname is resolved to the external IP. And I was mistaken, using the IP address rather than the hostname does actually work too (not sure why it didn't work once, but works fine now).

    I tried turning 3G on and off, and yeah, I can't connect when 3G is off. So it looks like the Lumia will use wifi but if it can't resolve an address, tries 3G instead?

    P.


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    #4
    ED E
    Registered Users Posts: 36,167 ✭✭✭✭ED E


    Yeah, its doing a smart failover so.

    If you have a Cisco 3925 you could bridge in a new router to get hairpin NAT working, but if you've any other modem no dice.


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