Internet drops out when LAN connected (Mandriva 2007)

lizparnell · 05-14-2007, 07:12 AM

Hi all,

We're having a strange problem with our Internet connection. The setup is 2 machines (one PC and one laptop) - the PC is connected to the Internet permanently via an ADSL modem (eth0), and the laptop connects to the PC via a direct cable connection (eth1). eth0 uses DHCP, eth1 uses static IPs.

The problem - when the laptop is not connected to the PC, everything is fine. However as soon as the laptop is connected, the Internet connection drops out intermittently. It happens around every 5-10 minutes (though it's not at all predictable), and reconnects itself automatically after a few seconds.

What should we be looking at? Shorewall is running on the PC - is it possible that it is not configured correctly or something?

Any suggestions/ideas welcome.

TIA,

Mark and Liz

Matir · 05-15-2007, 12:32 AM

As a guess, the computer is detecting this new connection and setting it as the default route until shorewall tries to bring the internet back up... sortof a back-and-forth. Can you get a copy of 'route -n' both with and without it working to verify?

lizparnell · 05-15-2007, 05:01 AM

When eth0 drops out:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
169.254.0.0     0.0.0.0         255.255.0.0     U     10     0        0 eth1
10.0.0.0        0.0.0.0         255.0.0.0       U     10     0        0 eth1
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         10.0.0.1        0.0.0.0         UG    10     0        0 eth1

When both are connected:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
169.254.0.0     0.0.0.0         255.255.0.0     U     10     0        0 eth1
10.0.0.0        0.0.0.0         255.0.0.0       U     10     0        0 eth1
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         58.106.209.128  0.0.0.0         UG    10     0        0 eth0
0.0.0.0         10.0.0.1        0.0.0.0         UG    10     0        0 eth1

When LAN is not connected:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         58.106.209.128  0.0.0.0         UG    10     0        0 eth0

Hope that tells you more than it tells me. ;-)

Thanks.

lizparnell · 06-01-2007, 04:40 AM

Just ran a quick test, and it appears that shorewall is not the culprit - I disabled shorewall temporarily, and the connection still dropped out.

Not sure if it's related, but the laptop couldn't connect to the Internet at all though with shorewall not running, even when the PC was connected fine.

Anyone got any bright ideas? I'm leaning towards a clean install on both machines (probably about time anyway), though the PC's DVD drive has died, so I'd have to replace that first.

In the meantime it's really frustrating!