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APIPA question

Discussion in 'Network+' started by robbo1962, Nov 6, 2007.

  1. robbo1962

    robbo1962 Byte Poster

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    I know Windows has an Automatic Private IP Addressing feature where an IP address is automatically assigned if a DHCP is not available and that Windows chooses an IP address in the range 169,254,x,y . My question is this, what is the main purpose of this as with this IP address you will not be able to access a WAN as the default gateway will be different and you will only see others on your LAN if they too cannot access a DHCP? Is it used primarily as a diagnostic aid or for just users who only use a LAN? Thanks Gary
     
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  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    It allows the quick assembly of a local lan (not connected to the Internet) without elaborate messing with configuring.

    Harry.
     
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  3. robbo1962

    robbo1962 Byte Poster

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    Thanks Harry
     
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  4. onoski

    onoski Terabyte Poster

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    As a matter of fact APIPA is just a fancy TCP/IP tool thought up by Microsoft as it does not achieve much with regards to network resource access.
     
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  5. BosonMichael
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    BosonMichael Yottabyte Poster

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    Actually, all Microsoft did was come up with a cute acronym. The actual standard and functionality is defined in RFC 3927, called IPv4 Link-Local (IPV4LL).

    That said, I agree that it doesn't achieve much with regards to networking.
     
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  6. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    To be fair - it is actualy a fairly useful system. It is quite frequent that people need to put together a quick network, particularly in business meetings. Without APIPA it would be a nightmare of changing settings on everybodies machines, and coordinating it all.

    With APIPA it 'just happens'.

    I note that Apple thought it sufficiently good idea to include with Macs as well.

    And the range is properly allocated, and even appears in RFC3330 as a 'special purpose range'.

    Harry.
     
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  7. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    But check who *wrote* the RFC! :biggrin

    Apple, Microsoft and Sun.

    Harry.
     
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  8. dales

    dales Gigabyte Poster

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    Also as you can change the default address provided for APIPA then it might be usful if you travel between 2 sites say work and home for which work has a domain and all the lovely extras that go with it and a home connection with static addresses.

    My network has statically assigned IP addresses for my workgroup at home (thats another story) but If I had a laptop for work and home purposes then I could set apipa to have an address in the correct home range and it would be allocated that when it can not find a dhcp server.
     
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  9. BosonMichael
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    BosonMichael Yottabyte Poster

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    Sun wrote it... Microsoft stole it and marketed the heck out of it... and Apple enclosed it in a shiny white rounded case with few buttons.
     
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  10. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Um - you have references for that? :biggrin

    Harry.
     
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  11. BosonMichael
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    BosonMichael Yottabyte Poster

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    Just going by company tendencies. :twisted: heeheehee!
     
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  12. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Ah - I wondered why it didn't match with any online account.... :biggrin

    Harry.
     
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  13. Modey

    Modey Terabyte Poster

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    I presume you mean the Alternate Configuration options? If you do, you aren't actually changing the APIPA range. Windows attempts to obtain an IP automatically, and if it can't then the Alternative Configuration takes effect. There are none of the restrictions like you get with an APIPA, it's as if you had defined static IP settings.
     
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  14. BosonMichael
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    BosonMichael Yottabyte Poster

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    If AOL had been involved, it would have simply "withered on the vine". :twisted:
     
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  15. dales

    dales Gigabyte Poster

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    yes thats what I ment, sorry!
     
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