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Sharing Internet Connection when ISP gives fixed IP - do not work properly

Discussion in 'Networking Issues' started by dlesisz, Apr 21, 2007.

  1. dlesisz

    dlesisz LI Guru Member


    Currently I’m using Linksys WRT54GL and Tomato 1.06 (I might also flash different firmware if this would solve my problem below)

    My ISP who gives me the same IP address to two different MAC addresses – so I can use those two computers (Desktop and Laptop) – but they can not work at the same time because of that.

    Hardware configuration looks like that:
    Ethernet socket --> WAN port on WRT54GL
    LAN port on WRT54GL --> laptop

    I can not split/share this internet connection properly. After making settings (details below in the post) I can ping to www.google.com or to any other website. I can do it using router feature Tools/Ping or if I do pinging from laptop.

    It would mean that I have connection to external world via this router.

    BUT any www or any telnet or any ftp do not work – nothing ….

    My goal is to share the Internet Connection to laptop and desktop in a way when both could work simultaneously.

    INTERESTING thing is that when I use ICS (Internet Connection Sharing) on my desktop with AnalogX (proxy software) – both computers might work simultaneously without any problems.

    Configuration looks here like that:
    Ethernet socket --> router (LAN port) --> cable to NIC @ desktop and - - > laptop via WiFi connection.

    Of course disadvantage of this solution is that desktop has to work all the time.

    The goal is to configure network in a way when Router will share internet connection (and not desktop via proxy)

    I do not know what protection is on ISP site (if any) – but I’d like to try to find walk around. I red about possibilities for ISP to discover that user is sharing connection – but also about different ways to walk around it and hide the fact. All articles I saw were saying that it is anyway possible – but I couldn’t find instruction.

    Maybe this is only wrong setting in my router and Tomato firmware.

    Anyone could help with that problem?

    My HW configuration looks like that:

    MAC Address 00:07:C6:57:C1 (This MAC is registered to ISP)
    Connection Type DHCP
    IP Address
    Subnet Mask
    MTU 1500

    Router MAC Address 00:14:BF:6A:C3
    Router IP Address
    Subnet Mask
    DHCP - 149

    I’ve tried to change TTL to "none" and to +1 – didn’t help
    I’ve tried to set smaller MTU

  2. ifican

    ifican Network Guru Member

    If the isp has registered the mac's in question then you need to "spoof" the mac of the router to match one of them. As far as connectivity goes, try taking the dns entries you get from you isp and plugging those into the your router under the local lan settings. If that doenst work report back and we can go from there.
  3. dlesisz

    dlesisz LI Guru Member

    Thank you for answer.

    I've used one of two MAC's registered to ISP and put it into the router.

    The router has DHCP settings (as my desktop had) and it gets IP address and DNS addresses automatically from ISP.

    When I look at router overview feature - it gives proper information.

    I was also trying to set all the same settings into the router manually (as you suggested) - but the result was exactly the same.

    ping from laptop connected to router works and also works from router ping tool - but I can not browse any website still from laptop. (if I remove router and refresh IP in laptop - all works perfectly).

    PS. I'd like to also mention that I was trying to play with TTL settings in router. I was trying to add "+1" to TTL, also remove "-1" from TTL value. I've also created script to set TTL always to 64 or always to 128 - but this also did not help. That move was adviced by a friend of mine)

    If there are any other ideas - I'm more than happly to test them here.


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