Posts Tagged ‘network’

Fix e1000e: Detected Hardware Unit Hang

Having periodic connectivity issues and seeing this in your dmesg?

e1000e 0000:02:00.0: eth0: Detected Hardware Unit Hang:
  TDH                  <a2>
  TDT                  <8e>
  next_to_use          <8e>
  next_to_clean        <a2>
  time_stamp           <214ed55a5>
  next_to_watch        <a2>
  jiffies              <214ed6d98>
  next_to_watch.status <0>
MAC Status             <80080783>
PHY Status             <796d>
PHY 1000BASE-T Status  <7800>
PHY Extended Status    <3000>
PCI Status             <10>
e1000e 0000:02:00.0: eth0: Reset adapter
e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: Rx/Tx

This occurs during normal operation of some 82573-based NICs due to a problematic power saving feature. Fortunately, this can be fixed permanently by altering the NIC’s EEPROM. If your card is affected you will see the value 0xDE in the second-last position of the second line when you run:

# ethtool -e eth0
Offset          Values
------          ------
0x0000          00 00 00 00 00 00 30 0b 46 f7 07 10 ff ff 00 24 
0x0010          ff ff ff ff 6b 22 f9 02 14 10 8c 10 86 80 de ac

This value must be changed to 0xDF to disable the feature, which can be accomplished using this bash script:

# ./ eth0
eth0: is a "82573E Gigabit Ethernet Controller"
This fixup is applicable to your hardware
executing command: ethtool -E eth0 magic 0x108c8086 offset 0x1e value 0xdf
Change made. You *MUST* reboot your machine before changes take effect!

Mounting an NFS Share on OS X: There was a Problem Connecting to the Server

You’ve tried to mount your linux NFS share via the Go menu’s Connect to Server dialogue but you keep getting an error message stating:

There was a problem connecting to the server

There was a problem connecting to the server

You know your URI is formatted correctly (nfs://server/share) and you can mount the share on other Linux hosts so what gives?

It turns out that in order to get OS X to play ball we have to add insecure to the export options of the shares you would like to mount. For example:


Configure Stand-Alone Bridge on Debian

I like to start my Xen networking by creating two (or more) bridges, one connected to the physical interface on the dom0 and another which is only connected to by virtual machines. This lets me set up an internal private network for cross-VM interaction and administration which is insulated from the DC’s network. If you put a router VM on both bridges which occupies your public IP addresses you can use 1-1 NAT to stack services from different VMs behind one IP and firewall the virtual machines. This is particularly handy where your address space is small but your VMs are many.

Unfortunately, the Debian interfaces configuration scheme doesn’t like setting up bridges with no bridge_ports directive so we have to give it a little boost. You will end up with a configuration file that looks something like this:

auto lo
iface lo inet loopback

iface eth0 inet manual

auto extbr0
iface extbr0 inet static
        bridge_ports eth0
        address x.x.x.x
        network x.x.x.0
        broadcast x.x.x.255
        gateway x.x.x.1

auto intbr0
iface intbr0 inet manual
        pre-up    brctl addbr $IFACE
        post-down brctl delbr $IFACE
        up        ifconfig    $IFACE up y.y.y.y
        down      ifconfig    $IFACE down

Where y.y.y.y is an internal IP you can use to access the dom0. For example you might prefer not to expose SSH on your dom0 to the wild, you would make sshd listen on this IP and shell in over a VPN.

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