Wired connection can't reach internet after wireless connection

[Dale Manwiller]

When I move my Thinkpad with Ubuntu 7.10 from my home wireless network connected to Comcast Cable to my office wired network, Firefox consistently fails to connect to the internet. By using if config up and if config down and dhclient eth0 I can sometimes get internet connectivity reestablished. The process is somewhat unpredictable.

I have a dual boot system and windows does not have this problem so I don't think it is hardware. It seems to be DNS related but that is only a guess.

The Roaming box is checked in the wired network.

[Mauricio Peñaloza S. (elkan76)]

Wich wireless chip do you have?
Do you try these commands on a terminal:
sudo /etc/init.d/networking restart
sudo /etc/init.d/networking force-reload
After connecting to wifi

[Dale Manwiller (dmanwiller)]

MauroP,

Thanks for the timely response. I wasn't clear. The problem occurs on
the wired connection. It works fine on wireless but when I later
connect to a wired connection it fails to find the internet. When I
move from wired to wireless there is no problem.

I have not tried the two commands you listed. I will try them when I
move to a wired connection and let you know what happens.

My wireless chip is the PRO/Wireless 3945ABG Network Connection and I am
using the proprietary driver from the Ubuntu site.

Thanks,
Dale

MauroP wrote:
> Wich wireless chip do you have?
> Do you try these commands on a terminal:
> sudo /etc/init.d/networking restart
> sudo /etc/init.d/networking force-reload
> After connecting to wifi
>
> ** Changed in: ubuntu
> Assignee: (unassigned) => MauroP (elkan76)
> Status: New => Incomplete
>
>

[Dale Manwiller (dmanwiller)]

MauroP,
  When I use a wireless connection, Ubuntu assigns eth1 as the connection
device. I noticed the two commands you suggested work with eth0. Is there
a way to make them work with eth1?

Thanks,
Dale

On 2/27/08, MauroP <email address hidden> wrote:
>
> Wich wireless chip do you have?
> Do you try these commands on a terminal:
> sudo /etc/init.d/networking restart
> sudo /etc/init.d/networking force-reload
> After connecting to wifi
>
> ** Changed in: ubuntu
> Assignee: (unassigned) => MauroP (elkan76)
> Status: New => Incomplete
>
> --
> Wired connection can't reach internet after wireless connection
> https://bugs.launchpad.net/bugs/195975
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in Ubuntu: Incomplete
>
> Bug description:
> When I move my Thinkpad with Ubuntu 7.10 from my home wireless network
> connected to Comcast Cable to my office wired network, Firefox consistently
> fails to connect to the internet. By using if config up and if config down
> and dhclient eth0 I can sometimes get internet connectivity
> reestablished. The process is somewhat unpredictable.
>
> I have a dual boot system and windows does not have this problem so I
> don't think it is hardware. It seems to be DNS related but that is only a
> guess.
>
> The Roaming box is checked in the wired network.
>

[Mauricio Peñaloza S. (elkan76)]

Ok, I see that you don't have a "normal" trouble ;)
Well, if your wired connection have DHCP, you must try in your terminal: sudo dhclient

If you have static address, open the network-manager and insert the IP asigned, and then restart the network (command on the previous post).
This command ask for a new IP in the wired and wireless connection, and the first to gives it, is the new network to be attached. The previous commands works on both interfaces.

[Dale Manwiller (dmanwiller)]

Thanks for your suggestions. I had both wired and wireless set for "
Enable Roaming Mode". Apparently this mode didn't recognize the change
of DNS server when I went from wireless to wired. Dale

MauroP wrote:
> Ok, I see that you don't have a "normal" trouble ;)
> Well, if your wired connection have DHCP, you must try in your terminal: sudo dhclient
>
> If you have static address, open the network-manager and insert the IP asigned, and then restart the network (command on the previous post).
> This command ask for a new IP in the wired and wireless connection, and the first to gives it, is the new network to be attached. The previous commands works on both interfaces.
>
>

[doobydave (dooby-dave)]

I experience the reverse of this - that is after connecting via wired ethernet, the wireless refuses to work (well, the wireless is fine, but there is a DNS error so updates and normal internet appear inaccesible)

I discovered today that disabling the wired network from within network manager applet restored the correct behaviour.

[doobydave (dooby-dave)]

This is on 8.04 64-bit with IPW3945 (or 3495 - can never remember)

Apologies for the necro-post.

[Ronald Teune (zeekoe)]

I have experienced exactly the behaviour as described by doobydave "I experience the reverse of this..."@2009-04-18 on a fresh install of Oneiric. Drove me crazy for a few days.
The problem is that all the local traffic is still being routed (or at least tried to) via the wired interface. Since the nameserver is set to the IP address of the router, DNS traffic will fail, as well as other local (192.168.1.x) traffic. IP-based internet traffic (skype or pinging IP addresses) will however continue. The eth0 interface will keep its IP-address, which is not a problem, but what is a problem is that somehow ubuntu tries to route traffic through it even when it's disconnected.

dmesg knows it:
[10327.863977] tg3 0000:09:00.0: eth0: Link is down

Output of lspci -v:
09:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5755M Gigabit Ethernet PCI Express (rev 02)
 Subsystem: Dell Device 01f9
 Flags: bus master, fast devsel, latency 0, IRQ 45
 Memory at f1ef0000 (64-bit, non-prefetchable) [size=64K]
 Expansion ROM at <ignored> [disabled]
 Capabilities: [48] Power Management version 3
 Capabilities: [50] Vital Product Data
 Capabilities: [58] Vendor Specific Information: Len=78 <?>
 Capabilities: [e8] MSI: Enable+ Count=1/1 Maskable- 64bit+
 Capabilities: [d0] Express Endpoint, MSI 00
 Capabilities: [100] Advanced Error Reporting
 Capabilities: [13c] Virtual Channel
 Capabilities: [160] Device Serial Number [snip]
 Capabilities: [16c] Power Budgeting <?>
 Kernel driver in use: tg3
 Kernel modules: tg3

The kind wireless connection doesn't matter: I tried three different cards...
Laptop is a Dell D630.

Might be related to https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/277063