network unreachable resolving 'ns5.apnic.com/AAAA/IN': 2001:dc0:1:0:4777::131#53: 1 Time(s)
    network unreachable resolving 'ns5.apnic.com/AAAA/IN': 2001:dc0:6000::1:8369:2#53: 1 Time(s)
    network unreachable resolving 'ns7.virtua.com.br/A/IN': 2001:12f8:1::10#53: 1 Time(s)
    network unreachable resolving 'ns7.virtua.com.br/AAAA/IN': 2001:12f8:1::10#53: 1 Time(s)
    network unreachable resolving 'ns8.virtua.com.br/A/IN': 2001:12f8:1::10#53: 1 Time(s)
    network unreachable resolving 'ns8.virtua.com.br/AAAA/IN': 2001:12f8:1::10#53: 1 Time(s)
    network unreachable resolving 'ns86.dotcomhk.info/A/IN': 2001:500:1c::1#53: 1 Time(s)
    network unreachable resolving 'ns86.dotcomhk.info/AAAA/IN': 2001:500:1c::1#53: 1 Time(s)
    network unreachable resolving 'nsauth1.argeweb.nl/A/IN': 2001:610:0:800d::2#53: 1 Time(s)

Edit /etc/sysconfig/network and set "NETWORKING_IPV6" to "no"
Add the following to /etc/modprobe.conf :

alias ipv6 off
alias net-pf-10 off
Run /sbin/chkconfig ip6tables off to disable the IPv6 firewall
Reboot the system
Alternative (which might be easier and works on any release with /etc/modprobe.d):

# touch /etc/modprobe.d/disable-ipv6
# echo "install ipv6 /bin/true" >> /etc/modprobe.d/disable-ipv6
With the 5.4 update symbol/ipv6 module dependency capabilities have been introduced; therefore, if IPv6 has been previously disabled as above an upgrade to the bonding driver in 5.4 will result in the bonding kernel module failing to load. For the module to load properly use instead:

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