In past versions of ubuntu, I’ve experienced slow connections specially with internet. And it’s been because of IPv6. Now in Ubuntu 10.04, I didn’t noticed any slow connection; however, I decided to go ahead and disable it anyways… just in case. And here are the steps.
Checking whether IPv6 is enabled or not.
jorge@nixboxen:~$ cat cat /proc/sys/net/ipv6/conf/all/disable_ipv6
cat: cat: No such file or directory
if output=0 then is enabled. So use your preferred editor and open /etc/sysctl.conf. Then add the following lines.
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1