[neutron] subnet policy for ip allocation

Ruslanas Gžibovskis ruslanas at lpic.lt
Mon Jun 22 10:42:28 UTC 2020

Hi all,

well, the problem here, for me, is that I do not manage switches from the
OSP part.
SO whenever I delete an instance, it frees up IP in the subnet, and that IP
is allocated to another machine, and thanks to the "arp table" feature in
the switch, switch send traffic to wrong compute as it remembers my
newly grabbed IP address on other port... and switches are very fancy, so
they do not have option to save arp for 1 min, 5 is the smallest amount.

I am just curious, am I only one who creates instances "so often"?

> Hi Ruslanas,
> The Neutron IP allocator does not do sequential allocation any more, it
> will choose randomly from a set of available IPs in the subnet.  So the
> odds of this happening are small, although not zero.  The only way to
> change this would be to write your own IPAM driver to do allocation in a
> specific way if that is required.
> -Brian

Ruslanas Gžibovskis
+370 6030 7030
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