Tethering via USB is an impossibly painful task

[Ken Sharp]

What I want to do is incredibly simple:

- I have my computer connected to eth1 which has internet access. This works fine.

- I want to connect another network to usb0, not permanently - when I need to use it, and use this for Internet access while remaining connected to eth1 as there are resources I still want to access on that network.

This appears to be impossible via the Network Manager applet. There is no logical sense to the routes chosen at all and editing the routes is even more of a mystery.

I gave up in the end and removed network-manager altogether. Adding a metric in interfaces solves it much more easily.

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth1
iface eth1 inet dhcp
metric 10

# Phone
auto usb0
iface usb0 inet dhcp
metric 0

There is no obvious reason why I would choose Network Manager on a desktop given that this simple functionality is apparently missing.

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ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: network-manager 0.9.4.0-0ubuntu4.4.2
ProcVersionSignature: Ubuntu 3.11.0-26.45~precise1-generic 3.11.10.12
Uname: Linux 3.11.0-26-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.8
Architecture: i386
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
Date: Fri Jan 23 11:26:30 2015
IpRoute:
 default via 192.168.0.254 dev eth1 proto static
 169.254.0.0/16 dev eth1 scope link metric 1000
 192.168.0.0/24 dev eth1 proto kernel scope link src 192.168.0.13 metric 1
 192.168.42.0/24 dev usb0 proto kernel scope link src 192.168.42.37 metric 1
IwConfig:
 lo no wireless extensions.

 eth1 no wireless extensions.

 usb0 no wireless extensions.
MarkForUpload: True
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
RfKill:

SourcePackage: network-manager
UpgradeStatus: Upgraded to precise on 2014-12-07 (46 days ago)
nmcli-con:
 NAME UUID TYPE TIMESTAMP TIMESTAMP-REAL AUTOCONNECT READONLY DBUS-PATH
 Wired connection 2 e02cf14b-492a-443f-9767-7b1a7e716f65 802-3-ethernet 1422012303 Fri 23 Jan 2015 11:25:03 GMT yes no /org/freedesktop/NetworkManager/Settings/1
 Wired connection 1 a7eb3b41-0730-4393-beec-dd11610b1ee5 802-3-ethernet 1422012303 Fri 23 Jan 2015 11:25:03 GMT yes no /org/freedesktop/NetworkManager/Settings/0
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH
 usb0 802-3-ethernet connected /org/freedesktop/NetworkManager/Devices/1
 eth1 802-3-ethernet connected /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 enabled enabled disabled