Comment 20 for bug 310035

I have the problem with karmic as well.
The machine connecting to the internet is not using network manager, but static configuration from /etc/network/interfaces

# The primary network interface
auto eth0
iface eth0 inet static
 address 10.15.0.1
 netmask 255.255.255.0
 network 10.15.0.0
 broadcast 10.15.0.255
#dsl-provider
iface dsl-provider inet ppp
pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf
provider dsl-provider

When upload on ppp0 reaches the ADSL limit, the server itself is no longer pingable (or high latency) on eth0. I can happily transfer at 100mbit in the internal network as long as ppp0 is not saturated, though.
The only relationship between ppp0 and eth0 is that eth0 is used to reach the ADSL modem.