Explain this to me...

Discussion in 'OT Technology' started by Leb_CRX, Aug 22, 2003.

  1. Leb_CRX

    Leb_CRX OT's resident terrorist

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    I do tech support, and I had a customer call me yesterday that could not get online...had him power cycle the modem and he's back on...no worries, what boggles my mind is this though, he has a old Dlink SWITCH (I made sure) and he has two computers on his network, both of which have the same IP address (assigned by DHCP) and they can both access the internet simulatiously...I had him run a speed test on one of them while at the same time I had him browse a differant website on the other one...

    how is this possible???? is it just one of those network things that should not be happening but happen anyways sometimes and cannot be explained?? someone shed some light :hs: :hs:
     
  2. Leb_CRX

    Leb_CRX OT's resident terrorist

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    oh ya the IP address was a valid public IP ... 24.x.x.x off the RR network...

    :eek3:
     
  3. Rob

    Rob OT Supporter

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    I would sum this up with :eek3:
     
  4. Penguin Man

    Penguin Man Protect Your Digital Liberties

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    The guy calling tech support was God. Duh.
     
  5. Leb_CRX

    Leb_CRX OT's resident terrorist

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    :hahano:
     
  6. Zourn

    Zourn 16-bit Ninja OT Supporter

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    Did both computers have the same LAN IP or WAN IP?
    Using a switch and Microsoft's INternet Connection Sharing Wizard would broadcast the same WAN IP and allow both to access the internet at the same time. It turns the machine that actually connects to the modem into a Gateway/Router for the other computers on the same network, but since there is only one actual connection to the net, they would both broadcast the same WAN IP.
     
  7. Leb_CRX

    Leb_CRX OT's resident terrorist

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    they both had the same valid road runner IP...24.x.x.x

    ya I am aware of the ICC, it makes the machine act like a NAT box, but generally you get a private class C address (192.x.x.x) with those.

    the way he had his setup was modem -> switch ->comp1+comp2

    :s
     
  8. Zourn

    Zourn 16-bit Ninja OT Supporter

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    Computers can have more than one IP.
    I have mine setup the same way as he does, three comps and a modem all plugged into a switch. My main Computer connects to the internet and acts as a gateway, any internal LAN acts show 192.168.x.x as its IP, but anything through the web will show up as 66.x.x.x. If my Laptop does something on the internal LAN it shows up as 192.168.x.y, but if does anything on the internet (which if you were using a monitor from a remote location would be considered through the web) it shows the same IP as the main comp, 66.x.x.x, because the laptop does not actually access the internet, it is the main comp and it just relays the info back to the laptop.
     
  9. Leb_CRX

    Leb_CRX OT's resident terrorist

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    that is called ICC in windows XP, what your describing is a NAT box (network address translation)...I know what your describing, I use to set it up on my windows9x using sygate software...pain in the ASSS with that O/S...and I know computers can have more then 1 IP...I setup a lan box with a linux box with 5 nic cards....that was 5 ips...it's
    #network cards= #ip

    I dont think your understanding me, your laptop does have the same IP as your 'main' computer to the internet, but that's infact because your main computer is as you said relaying that information...when in fact the laptop has a 192 IP...the main computer is a NAT box, the laptop makes a request, the main one fetches it and sends it back to the laptop (remembering it made the request), and oviously since the main computer is the one who's making the request it appears as though the same IP address...now this guy BOTH of his machines had the same ip address...NONE of them had a private address, they both had a 24 IP address, I am not playing guess work here, I didnt make him to go whatsmyip.com or anything, I had him read it to me from his ipconfig, and each of his computers only had 1 NIC card (for ICC you need 2 in the main machine)

    |eb_CRX
     
  10. Astro

    Astro Code Monkey

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    Doesn't each packet carry the MAC address? The only theory I can think of is the switch is smart enough to route data based off the MAC address instead of the IP address. Hmm... makes me want to fiddle with my IPs to try this out.
     
  11. Leb_CRX

    Leb_CRX OT's resident terrorist

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    yep the ARP tables keep the MAC ID of the devices, and from what I learned through network is only MACID is stored per IP, which I found even stranger...honestly this is not explainable in any ways...I am gonna email my cisco teacher to see if he has anything to say

    but ya dude if you have time, mess with it, see if you can come up with anything, who knows maybe we'll prove a few people wrong :eek3: :cool:
     
  12. The Bastard

    The Bastard Guest

    This can be easily replicated in DSL using PPPoE. I've had my modem in the uplink port and computers would then be in the switches available ports. Each would then sign in using the same pass which in turn has a static ip routed to it, thus both were showing the same ip simultaneously.
     
  13. Zourn

    Zourn 16-bit Ninja OT Supporter

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    OK, I figured you were using the ISP's software to monitor his activity by his account and reading the IP from there. (I generally never trust customers to give me info.)

    As far as the ICC, I think we are both talking about something different. I run a shared DSL connection through my network to any computer that has the Main comp's IP set as the Gateway and DNS server. I run this with only one NIC card. I just checked, though, and oddly enough both my connections show a diff MAC.
     
  14. The Bastard

    The Bastard Guest


    username is assigned 1 static ip so radius always assign the same one no matter how many times the login is used.
     

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