If IPV6INIT is set to "no" in an interface's ifcfg file, dhcp6c will still get called. This seems incorrect. IPV6INIT = "no" should disable IPv6 for that interface and the ifup-eth script should honor that. Here is the relevant code form ifup-eth: # IPv6 initialisation? /etc/sysconfig/network-scripts/ifup-ipv6 ${CONFIG} if [[ "${DHCPV6C}" = [Yy1]* ]] && [ -x /sbin/dhcp6c ]; then /sbin/dhcp6c ${DEVICE}; The ifup-ipv6 script actually checks the value of IPV6INIT, and if it is not set to "yes", the script exits. Regardless of what ifup-ipv6 does, ifup-eth will continue to run dhcp6c. Bottom line that that I would expect IPV6INIT="no" to prevent dhcp6c from being run.
You have conflicting configuration - you've explicitly configured dhcp6c to run.