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Old 09-14-2004, 02:34 PM   #1
LQ Newbie
Registered: Sep 2004
Distribution: Debian Sarge
Posts: 3

Rep: Reputation: 0
Strange cable modem problem in Debian

Hi! I'm new here, and very new with Linux too, so please be patient with me.

I have a very strange problem. I recently installed Debian Sarge on my computer, and old Celeron 600-something MHz box. I connect to the internet via a cable modem connected to my ethernet card. My internet connection requires me to go to a certain website and log in there to access the rest of the net.

Now to the problem: after installing Debian from a CD image downloaded a couple of weeks ago, my ethernet card was detected ok and i could connect to the internet without any further configuration. I did a dist-upgrade with apt-get and rebooted. Now the boot sequence shows something about the ethernetcard not being ready, or not available or something like that. I couldn't figure it out, so since i hadn't configured anything i did a clean reinstall. Now my connection worked flawlessly again. This time i did a regular upgrade with apt-get, thinking perhaps things would work this time. After rebooting, everything was fine, but at the end of my session i noticed that i could not access the login website to log out. I could access different websites though. After rebooting again, i can't connect to the login website (and thus not to any website). I get the bootup message about the ethernet card not being ready again. The card is ok though, as i can connect to the internet from my Windows partition.

Running ifconfig returns something like this:

eth 0 Link encap:Ethernet HWaddr 00:02:44:12:04:59
inet addr: Bcast: Mask:
RX packets:2924 errors:0 dropped:0 overruns:0 frame:0
TX packets:46 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:180771 (176.5 KiB) TX bytes:4112 (4.0 KiB)
Interrupt:11 Base address:0xc800

lo Link encap:Local Loopback
inet addr: Mask:
RX packets:84 errors:0 dropped:0 overruns:0 frame:0
TX packets:84 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4296 (4.1 KiB) TX bytes:4296 (4.1 KiB)

I can even ping the ip-address of the login website, so i seem to be connected to it, but when trying to connect to it with a webbrowser, it just times out. It's not a DNS problem, as i type the ip address directly into the browser window. The ethernet card seems to be a RealTek RTL8139, at least that's whats found by linux according to the system log.

I can't for the life of me figure out what went wrong. I would be very grateful if someone could help me with this.
Old 09-14-2004, 02:48 PM   #2
LQ Newbie
Registered: Feb 2004
Posts: 25

Rep: Reputation: 15
Can you ping an other website?
And try a lower MTU value, something like 1452. I had the same problem when connection with a cable modem. To do that edit the file /etc/network/interfaces. there is something like:

auto eth0
iface eth0 inet static
! address 192.168.x.x
! netmask
! network 192.168.x.x
! broadcast 192.168.x.255
! gateway 192.168.x.x

!=probably not
mtu 1452

restart the network with(being root):

cd /etc/init.d
./networking restart

Hope this helps.

Old 09-14-2004, 02:57 PM   #3
LQ Newbie
Registered: Sep 2004
Distribution: Debian Sarge
Posts: 3

Original Poster
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No, i can only ping the login website, which makes sense. Actually, when i tried it just now, i couldn't ping that either, but after following your advice, i could ping it again. Still can't connect though.
Old 09-14-2004, 03:31 PM   #4
LQ Newbie
Registered: Jan 2004
Location: Pine Bluff, AR
Distribution: Ubuntu
Posts: 15

Rep: Reputation: 0
I agree that it doesn't sound like DNS, but just to close the issue for good, can you ping your DNS server(s)? What's the roundtrip time?

Anything new in your firewall config? You might try changing all the policies to ACCEPT for the time being. I'd be surprised to find that change anything, but it's worth a shot.

The only other thing I can think of at this moment is, after booting, open the terminal and turn eth0 off, then on again (ifdown eth0; ifup eth0). It would be really stupid if this fixes it, but I'm sure we've all seen weirder.
Old 09-14-2004, 03:59 PM   #5
LQ Newbie
Registered: Sep 2004
Distribution: Debian Sarge
Posts: 3

Original Poster
Rep: Reputation: 0
Ok, i found the problem, and i'm very embarrased. I realized that both occurances of this problem coincide with setting up a firewall. Disabling it solved the problem. I guess it was too obvious.

Anyway, sorry for wasting your time and thank you very much for taking the time to help. On the bright side though is that i have learnt a lot about networks on linux.


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