openstack instance 无法得到IP，日志显示 Received DHCP NAK ,谁遇到过这种问题啊？
在horizon中可以看到分到了IP，系统日志中也显示分到了IP，但是实例得不到Ip。日志如下：
1.系统日志
Jun 05 11:50:46 openstack-icehouse dnsmasq-dhcp[25577]: DHCPDISCOVER(tape31caf30-ed) fa:16:3e:2e:0b:d6
Jun 05 11:50:46 openstack-icehouse dnsmasq-dhcp[25577]: DHCPOFFER(tape31caf30-ed) 10.5.1.212 fa:16:3e:2e:0b:d6
Jun 05 11:50:46 openstack-icehouse dnsmasq-dhcp[25577]: DHCPREQUEST(tape31caf30-ed) 10.5.1.212 fa:16:3e:2e:0b:d6
Jun 05 11:50:46 openstack-icehouse dnsmasq-dhcp[25577]: DHCPACK(tape31caf30-ed) 10.5.1.212 fa:16:3e:2e:0b:d6 host-10-5-1-212
Jun 05 11:50:49 openstack-icehouse dnsmasq-dhcp[25577]: DHCPDISCOVER(tape31caf30-ed) fa:16:3e:2e:0b:d6
Jun 05 11:50:49 openstack-icehouse dnsmasq-dhcp[25577]: DHCPOFFER(tape31caf30-ed) 10.5.1.212 fa:16:3e:2e:0b:d6
2.虚拟机console-log
Starting network...
udhcpc (v1.18.5) started
Sending discover...
Sending select for 10.5.1.212...
Received DHCP NAK
Sending discover...
网络架构是： neutron + ml2 + ovs
