no internet connection until I restart router

Thanks for your bug report.

Which Router (exact modell) are you using?

It might be usefull if you boot up ubuntu (do not restart router!), open a termin window and provide us the output of:

"sudo /etc/init.d/networking restart".

Actually it's not the router. If I restart networking it works.

When I type "sudo /etc/init.d/networking restart" I get this

$ sudo /etc/init.d/networking restart
Password:
 * Reconfiguring network interfaces... eth2: ERROR while getting interface flags: No such device
There is already a pid file /var/run/dhclient.eth2.pid with pid 134993416
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFADDR: No such device
eth2: ERROR while getting interface flags: No such device
eth2: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up eth2.
ath0: ERROR while getting interface flags: No such device
There is already a pid file /var/run/dhclient.ath0.pid with pid 134993416
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFADDR: No such device
ath0: ERROR while getting interface flags: No such device
ath0: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up ath0.
wlan0: ERROR while getting interface flags: No such device
There is already a pid file /var/run/dhclient.wlan0.pid with pid 134993416
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFADDR: No such device
wlan0: ERROR while getting interface flags: No such device
wlan0: ERROR while getting interface flags: No such device
Bind socket to interface: No such device
Failed to bring up wlan0.
RTNETLINK answers: File exists
run-parts: /etc/network/if-up.d/avahi-autoipd exited with return code 2
                                                                         [ OK ]

And the Internet starts working

Seems to be a problem with the dhclient.

Could you please add the output of:

1) ifconfig # (before and after you restart network)
2) cat /etc/network/interfaces
3) ps aux | grep dhclient # (before and after you restart network)

to the bug report?

I also found another user with that problem:

Feisty networking problem (has to start networking manually)
http://ubuntuforums.org/showthread.php?p=2542268

I have the same bug.
If i remove (comment all lines) avahi-autoipd it can work without restarting?
Where can i reject running dhclientd on start?
i have static ip.
my "interfaces" in attachment.

I am also having this problem. When I reboot my machine my networking does not work. If I do one the following of these it comes back up:

sudo dhclient eth1

or

/atc/init.d/networking restart

Definately a Ubuntu dhclient bug.

I share this issue. In, say, one out of every 10 boots I have no internet connectivity. If I reboot, it resolves the issue every time. Annoying.

I have the same or a similar bug. Whenever I reboot my Dell laptop, I can connect to the router, and even to the admin interface, but I can't access the internet until I restart the router. All other devices in my household, including a tablet, two smartphones, and another dell laptop also running Ubuntu 11.10 do NOT have this problem. Bizarre. Had the same problem with another router with I replaced. Not sure when the problem started but never had it on 11.04. I'm not even sure if it's an Ubuntu bug, some bizarre router behavior, or even a problem at the ISP. This bug looks very old, so I'd be surprised if it's really the same issue.

09:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5906M Fast Ethernet PCI Express (rev 02)
0c:00.0 Network controller: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection (rev 02)