Tag Archive: networking


KVM: Virtual Bridge (virbr0) is NOT needed! I show you how to remove it :)

Filed Under: libvirt / KVM, Linux, OS, virtualization by Jason L Froebe — Leave a comment
November 28, 2011

for KVM, using an actual network bridge is desired for performance over NAT. There is a virtual bridge used by XEN (virbr0) that you won’t need.
To disable it:

$ virsh net-destroy default
$ virsh net-undefine default

# If Redhat based distro:
$ service libvirt-bin stop
# if Debian/Ubuntu based distro:
$ service libvirtd restart  

$ ifconfig
 

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OpenVPN really really slow? This performance tip might help

Filed Under: How To by Jason L Froebe — 1 Comment
September 14, 2010

I use the virtual private network software, known as OpenVPN, to connect from my laptops to my home every day.  There are several things I’ve noticed:

  • Most offices and many coffee shops will block the default port 1194 (UDP).  It is also a very popular port for naughty people trying to see what you have on your network.  If you’re not running a web server, set it to port 80 or 443 (TCP) as these ports are normally accessible.  If these don’t work, try other ones like 21 (TCP) which is normally used for a FTP server.  You will likely see better throughput on some ports than on others due to ‘traffic shaping’, aka giving network priority to certain applications.
    • Comcast blocks ports 21,80,443 for UDP and but not for TCP
  • The network packets that are sent through the vpn tunnel can become fragmented, split into two or more packets to make them fit into the vpn network packet.  Let’s increase the size of the vpn network packet to reduce the network packet fragmentation
    • tun-mtu 1500
    • mssfix 1400
  • Compression.  This is a little more subjective than you would think.  If most of your activity is based on data streams (e.g. watching video, listening to music), then the compression may cause delays (think extra buffering / stuttering).   My advice is to try with it on and try with it off..  which seems to be more responsive to you?
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VMware – copied the Ubuntu vm but now the networking doesn’t work?

Filed Under: Linux, OS, VMware by Jason L Froebe — Leave a comment
June 24, 2008

You’ve probably seen it, you copied an Ubuntu Linux virtual machine under VMware and tried starting it up with a new VMware UUID and the networking doesn’t work.  When you use a new VMware UUID, it will change the mac address on any virtual network device you have configured in the virtual machine.

A very simple ‘fix’:

In /etc/udev/rules.d/70-persistent-net.rule, delete the entry for your network device(s) so the new mac address is recognized on reboot.  It will look something like so:

# PCI device 0×1022:0×2000 (pcnet32)
SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:0c:29:aa:4c:75″, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth0″

Your network devices will now be working.  Don’t forget to reboot your virtual machine.

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