Slow downloads in Linux? IPv6 may be to blame

Internet Protocol Version 6 (or IPv6 for short) promises to solve the problem of dwindling IP address. Long story short, we're running out of the roughly 4 billion addresses available to us under the current scheme (IPv4), so it's time for an upgrade.

Internet Protocol Version 6 (or IPv6 for short) promises to solve the problem of dwindling IP address. Long story short, we're running out of the roughly 4 billion addresses available to us under the current scheme (IPv4), so it's time for an upgrade. IPv6, in addition to providing several security and efficiency enhancements, provides on the order of 340 "undecillion" addresses (that's a lot, by the way). Sounds great, and it will be once we're all connecting to networks and hardware that make use of IPv6.

However, in Ed Tech, this probably won't apply to most of us for some time (new routers and managed switches certainly aren't in my budget). IPv6 rollout in the rest of the world can go on quite happily without affecting us, unless you, like me, have been dabbling in Linux. Linux, forward-thinking and super great set of operating systems that it is, generally supports IPv6 by default. As a result, when it's connected to an IPv4 network (like most of ours at home and school), it spends a fair amount of time resolving addresses. What this looks like to the end user is very slow page loads in a web browser, a surefire way to turn new users off and send them fleeing back to IE and Windows.

Fortunately, there is a quick fix for this problem that drastically speeds page loads (and is easily reversible once IPv6 becomes more prevalent). The first step is to type about:config in the Firefox address bar. A long list of configuration flags appears. Just type ipv6 in the Filter text box and double-click on the network.dns.disableIPv6 flag (it will be the only flag visible). When you double-click on it, its value will change to true and Firefox will only use IPv4 to resolve domain names. The performance improvement should be immediate.

You can also disable IPv6 system wide. This requires a few simple entries at the command line that modify a configuration file on your computer. I'll give specific instructions for SUSE 10.x, but a Google search of "disable ipv6 for *insert linux distro of your choice here*" should yield instructions for other distributions.

In SUSE, open a terminal window and type:

sudo echo "alias net-pf-10 off" >> /etc/modprobe.conf.local

When you hit enter, you should be prompted for the root password on your system.

Then type: sudo echo "alias ipv6 off" >> /etc/modprobe.conf.local

Any other performance tricks or tips? Let us know below. Speedy users are happy users.

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