[PLUG] Xubuntu-10.4: Network Manager Does Not See Wired Network

[Daniel Pittman]

Dale Snell <ddsnell at frontier.com> writes:
> On Sun, 24 Oct 2010 09:43:57 -0700
> Rich Shepard <rshepard at appl-ecosys.com> wrote:
>
>> I need help from you folks administering Ubuntu systems. On my wife's
>> laptop only the wireless connections are seen (here and in the
>> neighborhood). The topmost portion, wired networks, says there aren't any
>> although I have an ethernet cable connecting the box to the local router.
>>
>> I tried running NetworkManager and was told it's already running. Next, I
>> tried 'lfconfig -a' and saw eth0 as well as lo and wlan0. When I ran 'ifup
>> eth0' I saw 'Ignoring unknown interface eth0=eth0' which makes no sense to
>> me.
>>
>> What do I do to have the NetworkManager see the wired connection when a
>> cat5 cable is plugged in and all that interface to be used instead of the
>> wirelss one?
>
> This sounds depressingly familiar.  :-( I had this trouble myself, though on
> a laptop running Fedora, rather than one of the 'buntus.  Oddly, it only
> affected the laptop, and not the desktop, which was running the same version
> of Fedora and NetworkManager.
>
> Get into NetworkManager's preferences, and check IPv6 settings for your
> wired interface.  Dollars to doughnuts it'll be set to Automatic.  Set it to
> Ignore.  You may have to restart NetworkManager.
>
> The trouble seems to be that if you have NetworkManager set to accept both
> IPv4 and IPv6 connections, it _requires_ both to be running, or it won't see
> the interface.  If your router is IPv4 only (as mine is) then the IPv6
> connection is never made, and the interface never comes up.

Er, NM only establishes network *addresses*, and will never accept a network
connection with any protocol from anywhere.

Additionally, IPv6 will automatically configure a link-local network address
in the absence of any infrastructure, so unless you disable IPv6 in your
kernel entirely you would have an address found regardless of what your router
supports.


Now, you might have problems with other applications - that do make network
connections - if IPv6 is enabled, but that is not much to do with NM itself.

Regards,
        Daniel
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