Comment 1 for bug 1388117

This error message is produces because Neutron uses CT target:
https://github.com/openstack/neutron/blob/2cc3a780853686cc1fbf3123402cb7862c9bb12c/neutron/agent/l3_agent.py#L1613

which is not supported in CentOS 6.5 (NOTRACK target should be used instead). CT target was introduces in RedHat 7 with 3.10 kernel.