[openstack-dev] [Neutron][Nova][DHCP] Use case of enable_dhcp option when creating a network

Padmanabhan Krishnan kprad1 at yahoo.com
Wed Dec 17 08:15:34 UTC 2014

  Hello,I have a question regarding the enable_dhcp option when creating a network. 

When a VM is attached to  a network where enable_dhcp is False, I understand that the DHCP namespace is not created for the network and the VM does not get any IP address after it boots up and sends a DHCP Discover.But, I also see that the Neutron port is filled with the fixed IP value from the network pool even though there's no DHCP associated with the subnet. So, for such VM's, does one need to statically configure the IP address with whatever Neutron has allocated from the pool?
What exactly is the use case of the above? 
I do understand that for providing public network access to VM's, an external network is generally created with enable-dhcp option set to False. Is it only for this purpose?
I was thinking of a case of external/provider DHCP servers from where VM's can get their IP addresses and when one does not want to use L3 agent/DVR. In such cases, one may want to disable DHCP when creating networks.  Isn't this a use-case?
Appreciate any response or corrections with my above understanding.

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