dhclient continually seeks ip address on unconnected interface

Is this symptom still reproducible in 8.10 or 9.04?

Hi Daniel.

I re-enabled my eth0 (wired) connection and restarted networking, and am again seeing a steady stream of messages from dhclient every 4 minutes or so.

I'm on an up-to-date 8.10 system.

uname -a: Linux gandalf 2.6.27-9-generic #1 SMP Thu Nov 20 21:57:00 UTC 2008 i686 GNU/Linux

Regards,

Robert

Hi Robert,

What is the contents of your /etc/network/interfaces?

I had the following:

allow-hotplug eth0
iface eth0 inet dhcp

Which caused this to happen. This is on a Debian system, but I'd be surprised if it's not the same issue. My "fix" was simply to remove these lines and let network-manager handle the interface.

I would have expected ifupdown (guessing that's responsible) to be able to do cable sensing and not just keep trying.

I'm suffering this on 9.10, although I didn't on 9.04 and earlier. I suppose, in fairness, I'm suffering this issue on a connected interface, unlike the original reporter, although I think it's the same issue and it causes problems for me:

I connect to a network with a DHCP server and run:

sudo dhclient eth0

and all works fine; I have an address and do what I want to do. Then I move to a network without a dhcp server and run:

sudo ifconfig eth0 192.168.blah.blah/24 && sudo ip ro add default via 192.168.blah.blah

And all works fine again; I'm connected to my new network and do what I want to do. Until a few minutes later when (according to /vat/log/syslog) the address is dropped and dhclient tries to acquire a new one. It fails and I'm left unconnected. Running

sudo pkill dhclient

solves the problem. I have run this exact setup / procedures on 8.04, 8.10 and 9.04 without suffering this behavior from dhclient. It's particularly annoying!

joseph@joseph-work:~$ uname -a
Linux joseph-work 2.6.31-14-generic #48-Ubuntu SMP Fri Oct 16 14:04:26 UTC 2009x
joseph@joseph-work:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

Still true on Ubuntu 12.04. You get the DHCPDISCOVER log line constantly, until the disconnected interface is taken down.

Dec 8 18:35:33 hardhat dhclient: DHCPDISCOVER on eth3 to 255.255.255.255 port 67 interval 12
Dec 8 18:35:45 hardhat dhclient: DHCPDISCOVER on eth3 to 255.255.255.255 port 67 interval 7
Dec 8 18:35:52 hardhat dhclient: DHCPDISCOVER on eth3 to 255.255.255.255 port 67 interval 18
Dec 8 18:36:10 hardhat dhclient: DHCPDISCOVER on eth3 to 255.255.255.255 port 67 interval 9
Dec 8 18:36:19 hardhat dhclient: No DHCPOFFERS received.
Dec 8 18:36:19 hardhat dhclient: No working leases in persistent database - sleeping.
Dec 8 18:36:20 hardhat dhclient: DHCPRELEASE on eth3 to 192.168.1.1 port 67
Dec 8 18:36:20 hardhat avahi-autoipd(eth3)[2309]: Got SIGTERM, quitting.

I am getting this on Ubuntu 14.10. I have removed the eth0 lines from /etc/network/interfaces, but no effect.

I think I have the same issue on 14.04 Server, at least it appears to be the same issue. No network-manager.

If the server is configured for DHCP and you later change it to static, the dhcp client daemon still goes out and requests a DHCP address.

This impacts DNS for the device. The static IP remains on the interface, but the DNS record changes making it unreachable via hostname.

The work around that I found, other than killing the dhclient process, is deleting the dhcp client database and rebooting.
rm /var/lib/dhcp/dhclient.*

You could probably just kill the related interface files if you wanted to.

Based on the way this is behaving, I suspect its the same issue as not having the interface active.

I have a similar or same issue with Ubuntu 14.04.01 on a desktop with a Ethernet connection only that worked with Ubuntu 8.04 since 2006. Since updating, no internet.

I decided to upgrade and did a clean install of Ubuntu 14.04.01 trusty and I NEVER had Internet again on this dektop. I am sure (tested) that the cable is OK, the hardware is OK, the internet connection is OK

I have tried a lot of things and a long time spent with excellent support form the comunity in Italy via IRC did not solve the issue.

uname
Linux marco-desktop 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

dmesg|grep tg3
[ 1.156680] tg3.c:v3.134 (Sep 16, 2013)
[ 1.230990] tg3 0000:03:00.0 eth0: Tigon3 [partno(BCM95789) rev 4101] (PCI Express) MAC address 00:0f:ea:4c:4e:1a
[ 1.231000] tg3 0000:03:00.0 eth0: attached PHY is 5750 (10/100/1000Base-T Ethernet) (WireSpeed[1], EEE[0])
[ 1.231006] tg3 0000:03:00.0 eth0: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] TSOcap[1]
[ 1.231012] tg3 0000:03:00.0 eth0: dma_rwctrl[76180000] dma_mask[64-bit]

ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:0f:ea:4c:4e:1a
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
          Interrupt:18

interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

lshw -C network
  *-network
       description: Ethernet interface
       product: NetLink BCM5789 Gigabit Ethernet PCI Express
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: eth0
       version: 11
       serial: 00:0f:ea:4c:4e:1a
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.134 firmware=5789-v3.29a latency=0 link=no multicast=yes port=twisted pair
       resources: irq:18 memory:e4000000-e400ffff

lspci -nnk
00:00.0 Host bridge [0600]: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub [8086:2770] (rev 02)
 Subsystem: Gigabyte Technology Co., Ltd Device [1458:5000]
00:01.0 PCI bridge [0604]: Intel Corporation 82945G/GZ/P/PL PCI Express Root Port [8086:2771] (rev 02)
 Kernel driver in use: pcieport
00:1b.0 Audio device [0403]: Intel Corporation NM10/ICH7 Family High Definition Audio Controller [8086:27d8] (rev 01)
 Subsystem: Gigabyte Technology Co., Ltd GA-8I945PG-RH Mainboard [1458:a102]
 Kernel driver in use: snd_hda_intel
00:1c.0 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 1 [8086:27d0] (rev 01)
 Kernel driver in use: pcieport
00:1c.2 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 3 [8086:27d4] (rev 01)
 Kernel driver in use: pcieport
00:1d.0 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 [8086:27c8] (rev 01)
 Subsystem: Gigaby...

Marco B - Is only your loopback configured in /etc/network/interfaces? Whats the full contents of that file?

I have this in Ubuntu 14.04.3 LTS.

$ cat interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-driver nl80211
wpa-conf path_to_wpa_conf

I have the same problem in Ubuntu 14.04.3 too...here's my /etc/network/interfaces.

  # Localhost
  auto lo
  iface lo inet loopback

  ##########################
  # WAN - connected to MODEM
  ##########################
  # We use allow-hotplug here as otherwise get boot hang if modem down
  auto eth0
  allow-hotplug eth0
  iface eth0 inet dhcp

The problem comes and goes.