NetworkManager can't handle multiple interfaces, ppp0 to Internet and eth0 to LAN

[pramathesh ambasta]

I have set up a small LAN in our office. The LAN uses a switch to connect computers, some of them Ubuntu systems, with one another, to share files and printers.

The switch is connected to a broadband router which acts as a gateway to the Internet. So it is possible in normal situations for computers on the LAN to connect to each other *and* to the Internet without any problems.

Furthermore, these Ubuntu machines are also configured to connect to the Internet via a broadband USB modem when necessary. This option is used in one of two situations:

1. If the machine (laptop) is out of office and therefore not connected to the LAN
2. If the broadband router collapses due to some technical snag and is unable to offer any Internet services.

It is situation 2 that I am bothered about. In this situation NetworkManager offers us the possibility of working either on the LAN or on the Internet via the USB modem but not both. So if you want to surf the web, you have to disconnect from the LAN. If you want to use the LAN resources you have to disconnect the USB modem.

This should not happen. I have installed wvdial and gnome-ppp on the machines. By setting the defaultroute and replacedefaultroute options in /etc/ppp/peers/wvdial-pipe and /etc/ppp/peers/wvdial and not setting any DNS entry in the eth0 configuration, I am able to access both the LAN resources and the internet. This is the way it should be.

In my view, NetworkManager (or Modem Manager) is unable to replace the default route when it connects. In my experience, this has been a long standing problem in various Ubuntu releases ever since NetworkManager took over network configuration from ifup and /etc/networking/interfaces.

So my suggestion is that Ubuntu should use wvdial/gnome-ppp, take the pain away from setting setuid permissions from wvdial and configure it to replace the default route at the time of installation. NetworkManager could simply be a wrapper around wvdial to do this instead of trying unsuccessfully to reinvent the wheel.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: network-manager 0.9.4.0-0ubuntu4.1
ProcVersionSignature: Ubuntu 3.2.0-32.51-generic 3.2.30
Uname: Linux 3.2.0-32-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu14
Architecture: amd64
CRDA: Error: [Errno 2] No such file or directory
Date: Mon Oct 29 12:30:07 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
IpRoute:
 default via 220.224.141.129 dev ppp0 proto static
 220.224.141.129 dev ppp0 proto kernel scope link src 115.240.105.143
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=false
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.NetworkManager.NetworkManager.conf: 2012-06-16T13:13:51.230640
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH
 ttyUSB0 cdma connected /org/freedesktop/NetworkManager/Devices/2
 eth1 802-11-wireless unavailable /org/freedesktop/NetworkManager/Devices/1
 eth0 802-3-ethernet disconnected /org/freedesktop/NetworkManager/Devices/0
nmcli-nm:
 RUNNING VERSION STATE NET-ENABLED WIFI-HARDWARE WIFI WWAN-HARDWARE WWAN
 running 0.9.4.0 connected enabled enabled disabled enabled enabled

[Marius B. Kotsbak (mariusko)]

Upstream Network manager list discussion thread "Prioritizing between wwan and wlan" might be related to this problem.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.