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APIPA outside the LAN

Discussion in 'Networks' started by Boycie, May 6, 2006.

  1. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    Just had a call from someone who's computer is looked after by myself. Blimey, is that bad grammer or what!
    Anyhow, they have a USB ADSL modem which plays up from time to time (i have advised Connecting via a network card is prefered and at last they have agreed for me to replace it with a Netgear one!). This call was the usual *cant get on the Net*. Then they could then they couldn't.... At the time they called, according to the caller Network connections was displaying an APIPA address :blink .
    Now i know (i am studying hard for N+ :tune) you can't get outside your LAN when issued with an APIPA address so does anyone think the only possible explanation is the address is being cached in some way because of the *dropping in and out* of communication?
    As always your thoughts are appreciated :)
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  2. zimbo
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    zimbo Petabyte Poster

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    we talking about an IP thats issued by the ISP provider (DHCP server i assume?) ? If the connection is getting a APIPA address (169) then that means the modem is failing to connect or synchronize with the ISP...

    EDIT: could be a problem with the line.. or the USB (dont they also take a while to get their act together when first switched on?)
     
    Certifications: B.Sc, MCDST & MCSA
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  3. Boycie
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    Boycie Senior Beer Tester

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    yes, exactly what i thought Zim.... the modem connects directly to the ISP unlike something providing NAT which would display a Private IP. I think XP must be caching the APIPA and taking a little while to display the Public IP :biggrin
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  4. zimbo
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    zimbo Petabyte Poster

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    is the modem synchronizing? if its not them problem with the line or modem.. i really think this is a hardware problem and i got a feeling its the USB! :twisted:
     
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  5. Boycie
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    Boycie Senior Beer Tester

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    As Delboy used to say to Rodney... Zimbo, you know it makes sense.... :thumbleft
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  6. zimbo
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    zimbo Petabyte Poster

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    problem solved? :blink
     
    Certifications: B.Sc, MCDST & MCSA
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  7. Sparky
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    Sparky Zettabyte Poster Moderator

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    ipconfig/release

    ipconfig/renew


    Any joy? :biggrin
     
    Certifications: MSc MCSE MCSA:M MCSA:S MCITP:EA MCTS(x5) Security+ Network+ A+
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  8. _omni_

    _omni_ Megabyte Poster

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    i think if you have an APIPA address the computer will try every 5 minutes to contact a DHCP server.
    so while it doesn't "cache" it, it may take a few minutes before it automatically tries again. unless you do it manually, of course, like Sparky said.
     
    Certifications: MCSE 2003, MCSA:M
  9. Boycie
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    Boycie Senior Beer Tester

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    Thanks for the input guys. This has been an ongoing problem and i think i have narrowed it down to the USB ADSL modem so am going to swop it with a Nice Netgear router- via a NIC of course :)
    I'll let you know the outcome....

    Edit:
    As for Ipconfig/renew etc... i have never been there when it drops out (typical) and it only happens for a minute or two by all account...
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  10. r.h.lee

    r.h.lee Gigabyte Poster

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    Boyce,

    Questions:
    1) Is the "USB ADSL modem" actually a "USB ADSL router?" For example, my Efficient Networks Speedstream 5100 "DSL modem" actually is a NAT device, with DHCP capabilities. So what you might want to do is check if the "DHCP server" capability is enabled for configuration.
    2) Is the computer set to (*) Obtain IP address automatically? If so, then after a certain time period of not hearing back from a DHCP server, will the Windows computer resort to assigning itself an APIPA address. So by enabling a DHCP server ANYWHERE in the same broadcast domain as the computer should help to configure the computer's IP settings. The DHCP server doesn't even have to be the ADSL modem/router, for example a Windows NT Server 4.0 with a DHCP scope setup. Maybe by enabling the "DHCP server" feature for question 1 may solve your problem.

    I hope this helps.
     
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  11. Boycie
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    Boycie Senior Beer Tester

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    rh,

    no, it is a cheap and nasty free *thing* with an awful interface that has no NAT or DHCP facilities at all. It is the type of device that is useful to carry in your toolbox and that is about it. Being a USB only device it's own software configures literally everything and all you get to enter is the dsl account name and password. I am fairly confident it is that causing the problem as i left my trusted Netgear *testing* router there for a while and it never happened....
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  12. Jakamoko
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    Jakamoko On the move again ...

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    It does kinda sound like the modem, Boycey, but did you also check the obvious like USB cable, plug into different port, etc ? Also, was there any pattern to the drops at all ? Even like when someone was using a phone or watching Sky ? Even using a microwave or powerful outside light (laugh, I know, but once we pinpointed dropouts to a massive halogen spotlight outside a house that was causing enough interference when it switched on to drop the ADSL briefly - go figure ...)


    Just trying to be thorough (and hopefully helpful) :)
     
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  13. r.h.lee

    r.h.lee Gigabyte Poster

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    Boyce,

    Just some confirming questions, but do I understand that the "USB ADSL modem" can be replaced with another networking device such as your "Netgear router?" Then sounds like you need to recommend the client purchase a DSL router with DHCP capabilities. As you may or may not have come across in your Network+ studies, an APIPA address is non-routable. That's a required capability if you're going to be able to connect, or networkingly speaking, routed to the ISP and eventually to the Internet.

    Good luck.
     
    Certifications: MCSE, MCP+I, MCP, CCNA, A+
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  14. Boycie
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    Boycie Senior Beer Tester

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    Thanks for all the input guys :thumbleft I will keep you posted.

    Gav- Yeah, tried the usual; swopping ports, new filter, running with no other phone/equipment on line, interference etc.... looks like the modem is stuffed.

    RH- Yes the N+ does cover IP addressing and the fact that a local computer with an APIPA will stay local!

    Boyce
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  15. zimbo
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    zimbo Petabyte Poster

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    one other thing you could do is ask the ISP to release the customers IP address! - but has to be done from the telephone number the router is connected to unless its different policy in the uk...
     
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  16. Boycie
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    Boycie Senior Beer Tester

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    Zim,

    They are on a pool, but i think the modem is playing up- will keep you posted :thumbleft
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  17. zimbo
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    zimbo Petabyte Poster

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    check the line too so we can make sure...
     
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  18. Boycie
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    Boycie Senior Beer Tester

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    when i put my tester netgear router in all the line stats looked OK (with and without) the telephone plugged in. It also never failed while they were using my tester which is why i have ordered them one. Should be here Monday, Tuesday, so i'll let you know :thumbelft
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  19. zimbo
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    zimbo Petabyte Poster

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    so you ruled out the line? looks like you know alot about the netgear so if you see that the modem responds like it should but still gets APIPA then we can start looking at windows... :rolleyes:
     
    Certifications: B.Sc, MCDST & MCSA
    WIP: M.Sc - Computer Forensics
  20. Boycie
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    Boycie Senior Beer Tester

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    Just to keep you guy's informed, i installed the Netgear router Tuesday night and so far no problems reported. The user also reports that browsing the net seems quicker too...
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT

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