How to disable IPV6 on MacOs X 10.2 (Jaguar)



IPV6 seems harmless to people not using it. Usually it is. Some old network devices, however, may become mad because of early implementations of the protocol that are buggy (I have one of those :). So you may need to get rid of it if you are not using it. Another good reson may be your organisation's policy not allowing protocols not approved by management/techies in your network.

To switch it off on a modern linux machine is straightforward: just whipe it out from /etc/modules.conf and reboot. You achieve this by tuning the word "ipv6 " into " off". On M$ Windows it is disabled by default (at least to my knowledge).

SuSE linux 9.1 moved the /etc/modules.conf contents to /etc/modprobe.conf. Remember to delete the ::1 value of the inet_interfaces parameter in the /etc/postfix/main.cf file, otherwise the postfix subsistem will refuse to start.

In SuSE linux 9.2 beware that turning the line: 

alias sit0 ipv6
in /etc/modprobe.conf into: 

alias sit0 off
prevents telnet and rsh from working properly; for some mysterious reason the ptys tend to vanish from /dev.

Suse Linux 9.3 seems pretty similar to 9.2. You should add 

inet_protocols = ipv4
to the end of your /etc/postfix/main.cf file to avoid some annoying warnings from your postfix server.
You may wish to disable IPV6 from the configuration file that brings things up: /etc/sysconfig/network/config now bears an USE_IPV6= option that can be set to no. It drops ipv6 from ethernet interfaces leaving it alive only on the loopback, which may be mostly harmless.

On MacOs X 10.2 it is really easy: in the file /etc/hostconfig just change the line saying "IPV6=-YES-" turning it into "IPV6=-NO-" and reboot. Of course you have to be root to edit this file so you may issue from the terminal something like sudo your_favourite_editor /etc/hostconfig .

Of course, if you upgrade your system to Panther (aka MacOs 10.3) the IPV6 parameter will be reset to "-YES-", so you have to remember to change it once again.

If you upgrade to Tiger (MacOs 10.4) the /etc/hostconfig parameter seems to be totally ignored. You need to use the "network" panel in the System Preferences and disable IPV6 by setting it to Off in all the relevant interfaces in all the relevant profiles (called Location).

If you simply need to disable IPV6 just to see if it is doing something bad to your network without making the change permanent, all you need is to issue from the terminal application the command sudo ip6 -x (see man ip6 for details on ip6 command) and give your password as prompted.

Enjoy!