If you are using Ubuntu 11.04 or older version the most common problem that many users face is the slow browsing speed on Firefox browser. When you type any URL in the Firefox browser on the Ubuntu Linux operating system, it takes few seconds for Firefox to resolve the DNS and then the actual website is loaded. This means that every time you try to access the site there is a brief delay.
The issue is caused because IPv6 is enabled by default on Ubuntu. The IPv6 protocol was designed to replace IPv4, however most ISP’s are still not using IPv6 protocol. The Firefox browser in Ubuntu will first try the IPv6 protocol and when it fails the IPv4 protocol is used, hence the delay and slow browsing experience.
There are several posts on the internet that suggest one should disable IPv6 on Firefox browser. I tried that but that did not work. The best option I found was to disable IPv6 in the Ubuntu System itself.
Another problem with slow Firefox browsing was when using WordPress and adding an image to the post. When the image is selected and when you try to upload the processing gets stuck at 0% and the only way to get it going is to cancel the upload and try again. The second time the image uploads perfectly.
How to disable IPv6 in Ubuntu and increase internet speed.
The process is really simple. Load the terminal and copy and paste this line into the terminal.
gksudo gedit /etc/modprobe.d/aliases
Then when you see the edit screen add the following at the end of the file. In case the file is empty no problem just add the lines.
alias net-pf-10 ipv6 off
alias net-pf-10 off
alias ipv6 off
Once done save the file and reboot the system.
When the system starts again. Firefox will be much faster. Try it out and let me know if it worked. It did work for me.