Unknown host in my router's DHCP client list

Discussion in 'Network Routers' started by Michel S., Jul 9, 2007.

  1. Michel S.

    Michel S. Guest

    Hello !

    I have a small home network (3 PC's), all connected with cables to a
    D-Link DI-624 router.

    Each PC is configured in the router's DHCP with a static address.

    From time to time, a friend's come home and connects to the lan either
    with a cable, or with it's wireless adapter. In this latter case, I
    set the WiFi radio on. (Otherwise, it is always set to "off").

    Lately, I noticed a strange thing :

    In my router's DHCP dynamic client list, there's an "unknown" host
    listed. Unknown is both the host name and unknown to me.. The MAC
    address doesn't match with one of my pc's nor with my friend's one.

    Even if I shut down all but one of my pc's and reboot my router, this
    unknown client appears in the DHCP client list a few seconds later -
    with a lease expiring exactly one week from the moment I rebooted the

    I checked twice that my wireless radio was off.

    I do not use networked devices such as a stand alone printer with it's
    own print server.

    Any idea ?
    Michel S., Jul 9, 2007
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  2. Michel S.


    Are you using VOIP service?
    , Jul 10, 2007
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  3. Michel S.


    Does the router issue an IP address to unknown? If so, is it in the
    router's IP range (usually 192.68.x.xxx)? What operating system are you
    using on your computer?

    I think your question is a good one, because I have also seen mysterious
    clients show up in router device lists without explanation. Not always
    over wireless connections, either. Usually the whole thing becomes
    apparent after a little investigation, though.

    If the client shows up while the wireless function is disabled, it must
    be something hardwired to the router. Clear the connected devices list,
    disable wireless and use only your computer. See if the device shows up
    again under those conditions. If it does, the culprit is your computer
    (perhaps mis-identifying itself to the router's DHCP server).
    , Jul 10, 2007
  4. Michel S.

    John Dulak Guest


    Could it be that the WiFi interface is treated by the router just like
    a NIC and is assigned an IP address?

    I have a wired router with a WIFI access point connected to one of the
    router's wired ports. If the access point is NOT powered on, only
    wired connections show up in the router's DHCP client list. However,
    if I apply porew to the access point it shows up in the DHCP client
    list with its own MAC address and is assigned an IP address.


    '' Madness takes its toll - Please have exact change. ''

    John Dulak - Gnomeway Services - http://tinyurl.com/2qs6o6
    John Dulak, Jul 10, 2007
  5. Michel S.


    Well, not that I've ever seen. DHCP servers must be queried before
    issuing an IP, AFAIK. NICs just provide the interface, they don't
    actually need IPs. As I understand the OP, some device is requesting an
    IP even when the router's wireless function is disabled.
    Your WAP is acting just like any other client on the router's LAN. I'm
    guessing that any bridge or switch on the LAN would also require an IP
    address in order to function properly.
    , Jul 11, 2007
  6. Michel S.

    John Dulak Guest


    I understand that the NIC is just hardware and there must be software
    to request an IP address from the DHCP server. The wireless portion of
    the router must have SOME software associated specifically with it
    since it has to be able to forward packets, requests and, potentially,
    juggle multiple users.

    I guess my point is that poorly written firmware in the router might
    grab an IP address for the wireless port even if it is disabled.


    '' Madness takes its toll - Please have exact change. ''

    John Dulak - Gnomeway Services - http://tinyurl.com/2qs6o6
    John Dulak, Jul 11, 2007
  7. Michel S.


    I think that is a very good point and also goes a long way toward
    explaining why wireless connections can be so unreliable even after the
    IP is issued. I haven't yet run across a case like you are talking
    about, but I have seen stuff that I thought was just as weird.

    It seems like a good idea to eliminate all other possible causes before
    you go after the ones you can't directly do anything about, though. So I
    still think the OP should follow BAU troubleshooting steps to identify
    the IP interloper.

    I wonder also if interference devices (like cordless phones, microwaves,
    florescent lights, etc) could cause an 802.11b/g DHCP server to issue an
    IP? While looking online for info on Apple's "Interference Robustness"
    recently, I wound up reading a lot about the different ways in which the
    802.11 standard deals with interference, and I don't recall that
    particular issue being addressed. So, I don't know if it is even
    , Jul 11, 2007
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