Ubuntu 11.04 Server , CentOS5.6 : How to disable IPv6

Here’s an explanation of how to disable IPv6 on Ubuntu Server 11.04 or CentOS 5.6.

[ Ubuntu 11.04 Server : disable IPv6 temporarily ]

You can disable IPv6 all NICs or per NIC by editing under /proc/sys/.. or sysctl.conf

disable IPv6 on all NICs

root@ubuntu-1:~# cat /proc/sys/net/ipv6/conf/all/disable_ipv6 0

0 means IPv6 is enabled
1 means IPv6 is disabled

disable IPv6 per NIC ( /proc/sys/net/ipv6/conf/ethX/disable_ipv6 )

root@ubuntu-1:~# cat /proc/sys/net/ipv6/conf/eth1/disable_ipv6 0

disable IPv6

root@ubuntu-1:~# ifconfig eth2 | grep inet6          inet6アドレス: fe80::226:55ff:fee1:e83a/64 範囲:リンク root@ubuntu-1:~# root@ubuntu-1:~# echo 1 > /proc/sys/net/ipv6/conf/eth2/disable_ipv6 root@ubuntu-1:~# root@ubuntu-1:~# ifconfig eth2 | grep inet6 root@ubuntu-1:~# avahi-daemon[961]: Withdrawing address record for fe80::226:55ff:fee1:e83a on eth2.

enable IPv6 again

root@ubuntu-1:~# echo 0 > /proc/sys/net/ipv6/conf/eth2/disable_ipv6 root@ubuntu-1:~# ifconfig eth2 | grep inet6          inet6アドレス: fe80::226:55ff:fee1:e83a/64 範囲:リンク

[ Ubuntu 11.04 Server: disable IPv6 permanently ]

edit /etc/sysctl.conf

root@ubuntu-1:~# tail -6 /etc/sysctl.conf # disable IPv6 on all NICs net.ipv6.conf.all.disable_ipv6=1 # disable IPv6 on eth0 net.ipv6.conf.eth0.disable_ipv6=1

[ CentOS5.6  ]

# ifconfig eth0 | grep inet6          inet6 addr: fe80::6ab5:99ff:fe7c:9490/64 Scope:Link

at first , edit /etc/sysconfig/network file.

# cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no

second , make /etc/modprobe.d/disable-ipv6.conf file n’ add the following line.

# echo "options ipv6 disable=1" >> /etc/modprobe.d/disable-ipv6.conf

finally , reboot OS

After booting OS , IPv6 will be disabled.

# ifconfig eth0 | egrep -i inet6 #