Fritz DSL, DHCP/DNS problem, DNS does not show the hostname

Discussion in 'Linux Networking' started by Mattes, Mar 7, 2006.

  1. Mattes

    Mattes Guest

    Hi there,

    I try to convience my Fritz DSL Router to serve as a DHCP/DNS server.
    My problem is by booting windows (I apologize for this) I can do a
    nslookup and get the name of the host. Do I boot Linux on the same box
    I can't do this. When I check with the Fritz Web interface I can see
    that my IP and MAC is recognized but the name is "noname".

    Then I changed the /etc/dhclient.conf and included the name and MAC.
    # cat /etc/dhclient.conf
    send host-name "pimboli";
    send dhcp-client-identifier 00:04:76:48:57:05;

    Now I can see the hostname with nslookup within Linux and with the
    Fritz Web interface.

    Next time I boot the unspoken M$ pseudo OS I don't get an IP anymore. I
    have to reset the DSL box to factory defaults and then M$ is getting an

    Next boot, Linux! Same thing but other OS. I don't get an IP. Then I
    remove the entries from /etc/dhclient.conf and boot. All is fine except
    nslookup doesn't show the IP and hostname.

    It looks like DHCP is saving more then the MAC address. Under both OS
    hostname, MAC and the IP I get from DHCP is the same. The domainame is
    not set.

    What is wrong? Any ideas? Anybody with the same expirience?

    - FRITZ!Box Fon WLAN 7050, Firmware-Version 14.04.01
    - Laptop Dell Latitude C500, Kanotix 2005-04

    Mattes, Mar 7, 2006
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  2. Hello Mattes,

    is the following possible? Your linux box is lending out an ip adress from
    the dhcp server. This ip adress has got a lease time of e.g. 30 minutes.
    Now you boot your windows machine an the same mac adress
    (00:04:76:48:57:05) wants an ip adress with another hostname.

    Can you set the leasetime to a smaller value and test if this works better
    (after shutdown waiting until leasetime is over)?

    Short leasetime means more traffic because of more dhcp requests.

    Dirk Jakobsmeier, Mar 7, 2006
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  3. Mattes

    Mattes Guest

    Hi Dirk,

    I have tried your suggestion. The hostnames were already the same on
    Linux and Windows. In Linux I set the lease time to 60s but without any
    change in the result. On windows the lease time is around 10days. I
    couldn't find the Registry Key to change this.

    Or do you want me to use different hostnames?

    Mattes, Mar 7, 2006
  4. The lease time is not a client setting but a server setting, so you can't
    set it on either the Linux or the Windows box, you have to do it in the
    7050. Set a short lease time there and see what happens.

    What happens when you do a dhcp release before booting to the other OS?
    Does that change any of the behaviour that you see?

    Jan Hugo
    Jan Hugo Prins, Mar 9, 2006
  5. Mattes

    Mattes Guest

    Hi Jan Hugo,

    I thing I own you a beer. You put me on the right track.

    It looks like the DHCP release is not completly working under Windows
    or on the Fritz Router. On my Linux I see that at shutdown the DHCP
    lease is released. On M$ I can't verify that. But if I do on M$ a
    ipconfig /release I can boot Linux without a problem. So I would guess
    Windows is not doing a DHCP release. But on the other hand I would
    expect that the Fritz has to release a lease automaticaly because i.e.
    the server could have crashed before!

    So I'm not 100% sure who to blame! ;-)

    I found a work around for this by creating a little script which
    removes the dhcp-client-identifier from the configuration file, request
    an IP, release it and request it again with dhcp-client-identifier.
    Then I get an IP plus it is in the DNS of the Fritz.

    Thanks for putting me on the right track.
    Mattes, Mar 13, 2006
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