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ip address assignment rule

asked 2014-10-30 19:00:54 -0600

machi029 gravatar image

Let's say I have an IP Pool of -

I believe that the first VM instance will get the IP address "" The Second instance will get the IP address "" And the Third "" And so on... meaning I believe the default rule is ascending.

Is it possible to make this rule descending like... -> ->

Is there any configuration file to control the ip assignment rule?

I'm asking this because how openstack chooses the ip address was always a mystery for me...

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What kind of IP addresses you mean fixed ( via dnsmasq) or floating ?

DanIzack gravatar imageDanIzack ( 2014-10-31 02:51:32 -0600 )edit

fixed, via dnsmasq

machi029 gravatar imagemachi029 ( 2014-11-03 00:45:58 -0600 )edit

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answered 2014-10-31 00:01:17 -0600


  1. Generally first VM will get the IP instead of, since is gateway IP address, which is assigned to your bridge (generally br100).

  2. No we can't make it in descending way because DNSMasq service is going to take of this assignment.

OpenStack uses "dnsmasq" service to assign and manage IP addresses. When you boot your first instance you can see the "dnsmasq" service running on your machine by using "ps -Af | grep dnsmasq" you should get the output like:

root 3606 3605 0 10:14 ? 00:00:00 /usr/sbin/dnsmasq --strict-order --bind-interfaces --conf-file= --pid-file=/var/lib/nova/networks/ --listen-address= --except-interface=lo --dhcp-range=set:demo-net,,static,,120s --dhcp-lease-max=256 --dhcp-hostsfile=/var/lib/nova/networks/nova-br100.conf --dhcp-script=/usr/bin/nova-dhcpbridge --leasefile-ro --domain=novalocal --no-hosts --addn-hosts=/var/lib/nova/networks/nova-br100.hosts

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For 1. Thank you for pointing out that For 2. I guess I need to learn about dnsmasq more.

machi029 gravatar imagemachi029 ( 2014-11-03 00:47:47 -0600 )edit

Exactly... If that is possible in DNSMasq then you we use in OpenStack also. :) Good luck.

TechPatron gravatar imageTechPatron ( 2014-11-03 00:57:11 -0600 )edit

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Asked: 2014-10-30 19:00:54 -0600

Seen: 92 times

Last updated: Oct 31 '14