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  1. #1
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    How to find what IP's a DHCP has given out

    Hi All,

    In general, two questions:
    * Is there any generic method to find out what IP addresses have been assigned by a DHCP server?
    * Is there a generic way to force a DHCP server to dump a certain IP that was assigned, and/or force it to be renewed?

    Specifically:
    I have a DLINK EBR-2310. I can see what IP's were assigned dynamically, but I don't see any obvious way through the DLINk interface to dump it or force it to renew.
    Also, I have a Mac AirPort Extreme. I cannot see what IP addresses were assigned. I can only guess that the first one in the range was assigned, then check it by PING. If it doesn't work, I don't know if some other one was assigned, or if it is some other problem elsewhere.
    In both cases, I seem to be limited to what they allow you to do through the "pretty" interfaces. I am wondering if there are command line methods of doing these things.

    I am asking all this because I am trying to use an wireless internet radio appliance (Revo Pico), and I am trying various permutations of AirPort and/or LAN hub, to see which permutations works best/at all.

    Thanks!

  2. #2
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    Re: How to find what IP's a DHCP has given out

    I don't think there are any generic solutions to this, each device has its own management interface and different functionality.

    StuartR

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    Re: How to find what IP's a DHCP has given out

    Do you need to use DHCP? - perhaps assigning specific IP addresses may be an option.

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    Re: How to find what IP's a DHCP has given out

    Could the command-line program IPCONFIG assist here?

    Running it in a Command Prompt window on the PC using IPCONFIG /ALL gives all sorts of IP info.

    IPCONFIG /RELEASE followed by IPCONFIG /RENEW does what you might guess it does!
    <font face="Script MT Bold"><font color=blue><big><big>John</big></big></font color=blue></font face=script>

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    Re: How to find what IP's a DHCP has given out

    Hello Jim,

    Looking at the Dlink website, I found an emulator for your router.

    When accessed, there is a "tab" for SETUP across the top, and a selection of NETWORK SETTINGS on the left. The resulting display gives a table at the bottom of the view showing the DHCP address assignments.

    Is this what you're looking for?
    Christopher Baldrey

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    Re: How to find what IP's a DHCP has given out

    Hi All,

    Thanks for the responses!

    Regarding the DLINK emulator, true, you can see the IP's assigned by the DLINK on that page. However, this is true only for the IP's assigned by that device. Also, I am looking for a method to find out that is independent of the "pretty" interface.

    Regarding IPCONFIG, this will tell you the IP assigned to that particular machine. What I would really like is, a way to find out what IP's the DHCP server has assigned to each MAC, without having to look specifically at the server's "pretty" interface or by using a command on each specific machine.

    I am imagining, even though the DLINK and AirPort have their own "pretty" interfaces for the basic/most common functions, they both must implement DHCP to some level of standard. I am wondering if there is anything in the DHCP standard that allows (for example) a network administrator to ask a DHCP server (regardless of what hardware it resides on), "Hey, what IP addresses have you assigned, and to what MAC's?". PING works in a fashion like this - even though the DLINK and AirPort are different, they both respond to PING the same way (assuming you know what IP address to PING).

    Regarding whether I need DHCP or not, utlimately I don't need it, I can assign static IP's. However, I am using it to troubleshoot connection issues and narrow down if the problem I am having is setup or hardware, and where. Specifically, if I set a static IP on the radio, and the connection doesn't work, I don't know if it is the radio, the wireless, the DSL modem, etc. If I set the radio to use DHCP, and I use the DLINK as DHCP server, I can see what IP gets assigned. But if I use the AirPort as DHCP server, I can't see what IP address it assigned - I have to guess that it is the first one in the range I allowed.

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    Re: How to find what IP's a DHCP has given out

    Unless you have a reason to have two devices serving up DHCP, it's a bad idea.

    The airport device should be able to sit there, and act as a middle man. Taking the request for an IP address from it's near-by peers, and passing that information thru to the DLink box. I believe this is called bridging.

    Hope this helps....
    Christopher Baldrey

  8. #8
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    Re: How to find what IP's a DHCP has given out

    <hr>I am imagining, even though the DLINK and AirPort have their own "pretty" interfaces for the basic/most common functions, they both must implement DHCP to some level of standard. I am wondering if there is anything in the DHCP standard that allows (for example) a network administrator to ask a DHCP server (regardless of what hardware it resides on), "Hey, what IP addresses have you assigned, and to what MAC's?". <hr>

    It would be nice, but it definitely is not true. DHCP standards define how devices claim, renew and release addresses, but nothing to do with server administration.

    StuartR

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    Re: How to find what IP's a DHCP has given out

    Thanks! I am not using them both for DHCP server at the same time, but rather independently, one at a time, for troubleshooting purposes.

    Normally, I would use the DLINK for this purpose, since it is physically in the center of all these connections. (A Mac, a PC, and the AirpPort plug into one LAN socket each, the WAN goes to DSL). I wanted to try the AirPort as DHCP server, since the new device (radio) would be connecting via the AirPort wireless.

    My original question still stands.

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    Re: How to find what IP's a DHCP has given out

    With regard to your original questions, would Arp Viewer do anything to assist? It simply relates MAC addresses to IP addresses, and the results are considerably better than their webpage might indicate. However, their file identifying the manufacturers of NICs stopped 5 years ago (which is the date of the software).
    <font face="Script MT Bold"><font color=blue><big><big>John</big></big></font color=blue></font face=script>

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