There are lots of "lo: Disabled Privacy Extensions" in var/log/messages . I googled and find it is ipv6 releated, so I tried to disable ipv6. I added the following lines to /etc/sysctl.conf net.ipv6.conf.all.disable_ipv6=1 net.ipv6.conf.default.disable_ipv6=1 net.ipv6.conf.lo.disable_ipv6=1 and blacklist ipv6 to /etc/modprobe.d/blacklist.conf after that, I restarted the network by /etc/init.d/networking restart . My question is: The ip addr still shows inet6 address attached to eth0 in forms like inet6 fe80::212:79ff:fecf:edaf/64 scope link Does it means my ipv6 not disabled?