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      Where Are the First Two IPs?

      Q. When I ran this command:

      neutron net-ip-availability-show

      on my network to find out how many IPs I have available, I found that 29 were allocated to my project, but I wasn’t able to use the first two IPs. Why?

      A. The first two IPs are reserved for the the gateway IP and the fixed IP assigned to your router_gateway port, respectively. Specifically, in this example:

      # neutron net-ip-availability-show 0d13276b-c364-443a-9217-4af45e9e38f1
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------+
| Field                  | Value                                                                                                                                  |
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------+
| network_id             | 0d13276b-c364-443a-9217-4af45e9e38f1                                                                                                   |
| network_name           | external                                                                                                                               |
| subnet_ip_availability | {"used_ips": 29, "subnet_id": "46f82bc8-d180-46dd-9914-8733eddae793", "subnet_name": "external", "ip_version": 4, "cidr":              |
|                        | "153.122.122.160/27", "total_ips": 29}                                                                                                 |
| tenant_id              | 0a75d5b865224f1d8bcbf4fb59153c49                                                                                                       |
| total_ips              | 29                                                                                                                                     |
| used_ips               | 29                                                                                                                                     |
+------------------------+----------------------------------------------------------------------------------------------------------------------------------------+
      • 153.122.122.161 is reserved as the gateway IP for your external subnet of 153.122.122.160/27. It is also the Horizon IP.
      • 153.122.122.162 is reserved as the fixed IP assigned to your router_gateway port. This address is used to test the reachability of your Neutron router.

      These two IPs are essential to the operation of your OpenStack network and are unavailable for use by instances.