[openstack-dev] [neutron] Neutron should disallow /32 CIDR

Carl Perry caperry at edolnx.net
Tue Jan 21 21:26:16 UTC 2014

Using a /32 has use cases. When trying to build a L3 only routed network
/32 routes are required. While it can be inconvenient for the more
generic L2 network use case, I wouldn't remove it since there are other
use cases where it is useful.


On 01/21/2014 12:35 PM, Paul Ward wrote:
> Currently, NeutronDbPluginV2._validate_allocation_pools() does some
> very basic checking to be sure the specified subnet is valid.  One
> thing that's missing is checking for a CIDR of /32.  A subnet with one
> IP address in it is unusable as the sole IP address will be allocated
> to the gateway, and thus no IPs are left over to be allocated to VMs.
> The fix for this is simple.  In
> NeutronDbPluginV2._validate_allocation_pools(), we'd check for
> start_ip == end_ip and raise an exception if that's true.
> I've opened lauchpad bug report 1271311
> (https://bugs.launchpad.net/neutron/+bug/1271311) for this, but wanted
> to start a discussion here to see if others find this enhancement to
> be a valuable addition.
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