Cable Modem -> Router Problems

Posted on 2004-11-11
Last Modified: 2013-12-14
Equipment: Surfboard 4400 cable Modem, Dell ispiron 1100 running windows XP *, usrobotics wirless g router.
Problem: Cannot ping nodes external to the network, request times out. Have an 80 - 99% packet loss when pinging external gateway over an 8 hour period.

I have been systematically eliminating the possiblities for this problem.

I have replaced all cables
used 3 different laptops of different brands
replace my router 4 times ( 1 linksys, 2 cnets and now this usrobotics router)
I then took my router to a friends house with a cable connection and found that it worked an absolute treat. The only difference between our two connections was the brand of modem. So I rand My ISP and got a new modem, still no avail.

My main concern is that I can ping externally fine if i connect the cable modem directly to my laptop (no router) so the ISP doesnt want to have a bar of it and assertain it is my router. But the router works fine on a different connection provided by that same ISP!!!

I am nearly in tears!

From here I went round and stole my friends modem for a day much to his disgust and took it back and hooked it up on my connection, didnt work. So I am stuck thinking that it must be something to do with my ISP. But it cant be because the cable modem has a signal!


New Zealand
Question by:werdafucami
    LVL 41

    Expert Comment

    you say it doesn't ping, but does it surf?
    If so, is the router blocking port 7 (the echo port), both tcp and udp
    LVL 41

    Expert Comment

    the other thing to try is lower the MTU
    this refers to ICS but the theory is the same
    change MTU on client
    use drtcp to change the MTU settings
    drtcp (free)

    Author Comment

    Yeah changed the MTU several times and then put it back to default. No avail. And no it does not work for any port numbers : - ( any other ideas?
    LVL 41

    Accepted Solution

    Does it surf, can it fetch web pages?
    move the machine to the DMZ and test (to tell us if the router firewall is the problem)
    you have to reboot the router after moving the machine to the DMZ

    Author Comment

    Looks like I solved it:-)

    It turns out that it was my ip address xxx.xx.147.254. 254 was the highest it could be and caused an ip layer conflict of some sort. So I swaped my modem with my mates and it works a treat. The ISP is not happy with me, but screw em... they didnt help me.

    Thanks for your help!

    I did try the DMZ stuff but that didnt help either it was a good idea, so what the hell you get the points!


    LVL 41

    Expert Comment

    Glad you got it working, and thanks!

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