[Openstack] [Neutron][DHCP] vm can not get ip by dnsmasq

Brian Haley brian.haley at hpe.com
Wed Jan 4 18:24:57 UTC 2017

On 01/04/2017 03:22 AM, zhaolihuisky wrote:
> hi, all
> I have a problem about that vm can not get ip address by dnsmasq server.
> I have got the DHCP packets by tcpdump.
> With the DHCP protocol, client send DHCP Discover, and then server reply DHCP
> Offer, next client send DHCP Request and server reply DHCP ACK, at last vm get
> ip address.
> But in my openstack env, only one vm can not get ip address, and others could
> get a ip address.
> By analysing the DHCP protocol packets (see attachment), I found that vm send
> DHCP Discover, but dnsmasq didn't reply DHCP Offer.

Did dnsmasq log anything on receipt of the packet?  Does the host file in 
/opt/stack/data/neutron/dhcp/* have information for this VM?  Do you have any 
iptables rules that might be causing it?  I'm assuming the trace was taken 
inside the dhcp namespace so you know the packet got that far?

Since you can reproduce it with this one VM you can hopefully track it down, but 
there's nothing in your explanation that points at a particular issue in neutron.


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