internal ip keeps changing

Discussion in 'Network Routers' started by Linea Recta, Jan 6, 2010.

  1. Linea Recta

    Linea Recta Guest

    I have been portforwarding ports 20-21 in router setup for using my FTP
    Worked fine at first, but next day the PC ip seems changed and I have
    connection problems again.

    Anyone a clue how to proceed making a static ip?

    Afraid this is very confusing stuff. :-(
    Using a Sitecom WL-174, have a "manual" but it seems to be for experts...
    I found DMZ... do I use that??

    Also, in Windows XP I have been following this but it disabled my
    connection altogether. So I undid the changes.


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    Linea Recta, Jan 6, 2010
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  2. Linea Recta

    Rambo Guest

    In your router, you certainly, together with DHCP, have the possibility
    to have an option to give to a pc a static IP. This is done by creating
    a relation between his mac adress and the expected IP.
    You don't need DMZ which is a security hole.
    Rambo, Jan 6, 2010
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  3. Linea Recta

    Kerry Liles Guest

    Routers normally "hand out" IP addresses (via DHCP) based on a config
    parameter that defines the range of IPs that can be dished out. For example,
    if the router is the default setting may be to hand out IP
    addresses starting with (up to say)

    As the previous poster indicated, you CAN usually tell the router to give
    one of those specific addresses to a specific machine based on the MAC
    address of that machine... that is similar to a DHCP reservation - the
    machine requests an IP address (as most machines do) - the router determines
    that the machine's MAC address [which is unique] is in its table and always
    gives that machine the same IP address. This way, you KNOW what IP address
    that machine will always have.

    The alternative, is to change the machine to NOT use DHCP to request an IP
    address, but instead pick an IP address in the correct range (say - note that this address is NOT in the range that the router
    would normally hand out, but IS within the scope of the IP space managed by
    the router. This change is made in the network properties of the machine
    (the PC) that you want to have a static IP address. If you change things
    this way, you may need to make sure the other values normally supplied by
    DHCP (dns server, subnet mask, gateway IP etc) are correctly supplied.

    The link you gave to set up a static IP (at contains good
    info - if it disabled your connection it is likely because you pooched one
    or more of the settings - I would suggest following that info carefully!

    Kerry Liles, Jan 6, 2010
  4. Linea Recta

    Linea Recta Guest

    Thanks very much for the reply. I had been tinkering around to make this
    work finally. Succeeded in setting a static internal IP for the PC, but
    initially forgot to adapt the portforwarding rule to the new IP.
    At least now I still have normal internet access and FTP server also seems
    to work.

    Going to write this whole process down in a way I can grasp for future

    I do have a few other questions about some cryptic router options for which
    I hope to be back here asap.


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    Linea Recta, Jan 7, 2010
  5. Linea Recta

    Linea Recta Guest

    Thanks for the reply. By now I have made a static IP in Windows for the PC
    and made a portforward to this new IP.
    Is it still necessary to make a relation to a mac address? Don't know how
    this is done...

    I do have the mac adress filter enabled to enable access exclusively for my
    (2) other computers by wifi.


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    Linea Recta, Jan 7, 2010
  6. Linea Recta

    ray Guest

    No, because you choosed the second way of doing it. Assigning in the pc his
    own fixed ipadress.
    The relation(done in the router) between a fixed IP adress (fixed by the
    router) and the mac adress of the pc, is the first way of doing it. In this
    case the pc uses dhcp to get his ip adress.
    You may continue to use this simple protection way. However this protection
    is very low - someone can mimic your mac adress after sniffing it.
    I suggest to use a more secure protection, per example WAP2 based on AES
    with a phrase as a password.
    the phrase could be: "you never will find my password" :)
    ray, Jan 7, 2010
  7. Linea Recta

    Linea Recta Guest

    Additionally of course, I use WPA-PSK security. In fact this was one of the
    first things I got into when I started using a network. I found this much
    easier to comprehend than this "roaming internal IP" issue...

    WPA is the highest security level supported by my WM2003SE pocket PC.


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    Linea Recta, Jan 7, 2010
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