Hi,
all applications that need an Internet connection works very slowly, because of ipv6 I think. I disabled ipv6 in firefox and everything is ok now, but what about all others like wget, mail etc? How to permanently disable ipv6 in slackware 13.37, I tried blacklist ipv6 in /etc/modprobe.d/blacklist but it doesn't work. Help!

You can compile your kernel with your current .config without ipv6 support.

Is it not possible by any command or confing file?

I just blacklisted ipv6 in /etc/modprobe.d/blacklist.conf an I no longer have an IPv6 address in ifconfig eth0. I booted the machine, and it does not load.

Well, I have not IPv6 address, with or without blacklist ipv6. But I disabled ipv6 in firefox, which works normlany now, I thought that ipv6 is the problem, so why wget establishing connection last very long, the same situation is when I want to send email with sylpheed.

You can use ipv6.disable=1 as kernel command line parameter.

Having ipv6 enabled should not alter the speed of anything on a machine with only ipv4 network connections.

Perhaps your network has some ipv6 functionality but no actual ipv6 connection to the outside world, this would cause the problems you're describing.

You can use whizje's kernel option to disable ipv6 fully on a single system and is the simplest method

NB ipv6 is designed for complete auto configuration, if a router on a network is configured for ipv6 then every computer on that network that is ipv6 enabled will have ipv6 settings given to them by that router.

Just a quick confirmation, passing ipv6.disable=1 as kernel command line parameter does the trick.

One can do this by editing /etc/lilo.conf and adding after the line at the end of the file.

Of course, the "lilo" command has to be run after editing the file, and reboot.