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aioobe
Asked: 2010-11-05 00:44:53 +0800 CST

Ethernet / DHCP-trouble on Linux

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Have a strange problem with my wired network interface. Here goes:

  1. I plug in the cable.

  2. Both diodes light up (one green / one orange) and dmesg gives

    [   66.847512] tg3: eth0: Link is up at 1000 Mbps, full duplex.
[   66.847516] tg3: eth0: Flow control is off for TX and off for RX.

  3. nm-applet (network-management gnome applet) icon starts spinning, but gives up after a while.

  4. I terminate the nm-applet and try dhclient eth0 instead. This gives:

    $ sudo dhclient eth0
Internet Systems Consortium DHCP Client V3.1.2
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/eth0/00:16:d3:30:9e:73
Sending on   LPF/eth0/00:16:d3:30:9e:73
Sending on   Socket/fallback
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 4
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 10
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 14
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 13
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 13
...

  5. I thought it might be a hardware problem so I booted on a BSD usb-stick and I can ping fine back and forth.

  6. Back in Linux I tried with a USB-ethernet dongle, same result. Tried three different ethernet-connections. Same issue everywhere.

This is what ifconfig eth0 gives when I've plugged in the cable:

$ ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:16:d3:30:9e:73  
          inet6 addr: 2001:6b0:1:1de0:216:d3ff:fe30:9e73/64 Scope:Global
          inet6 addr: fe80::216:d3ff:fe30:9e73/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1056 errors:0 dropped:0 overruns:0 frame:0
          TX packets:19 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:244082 (244.0 KB)  TX bytes:4998 (4.9 KB)
          Interrupt:16

What could the problem be?

Update: Some extra information that may or may not be useful:

$ sudo mii-tool -v
eth0: negotiated 1000baseT-FD flow-control, link ok
  product info: vendor 00:08:18, model 24 rev 0
  basic mode:   autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
  link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD

...and...

$ sudo ethtool eth0
Settings for eth0:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supports auto-negotiation: Yes
    Advertised link modes:  10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Advertised auto-negotiation: Yes
    Speed: 1000Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: g
    Wake-on: g
    Current message level: 0x000000ff (255)
    Link detected: yes

PS: Wireless works just fine.

linux dhcp

2 Answers

  1. I ran wireshark on an existing connection to get an idea for the traffic that transpires. You can compare with your own.

    1. DHCP Discover goes out broadcast
    2. Within 5 seconds, a DHCP Offer is received from the DHCP server
    3. An DHCP request is transmitted by the initiator advertising at least the host's name
    4. DHCP server ACKnowleges the 2nd DHCP request
    5. Initiator started having layer 3 communications (IGMP and MDNS queries)

    That's all I needed and got. Not sure what else to give you. It might not be the host though. It is conceivable that the switch is having trouble with the IP it is trying to assign you. If you can register another device and then retry this host, you may find it.

    • 1

  2. Try connecting to another ethernet port. It seems like your DHCP request packets are not making it to the DHCP server or the DHCP server is misconfigured for the wired network.

    One other option, check to see if you are running any firewall that would stop the DHCP replies.

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