Here's what I get when I create a 4th subnet:

$ openstack network segment create --physical-network physnet_bo-az3 --network-type vlan --segment 1115 --network trust trust-az4
+------------------+--------------------------------------+
| Field | Value |
+------------------+--------------------------------------+
| description | |
| id | 92355e6d-3406-4b29-a956-1b05c4c9a33e |
| name | private-provider-trust-az4 |
| network_id | ac30a487-bccc-c3de-93eb-c422ad9f3ce5 |
| network_type | vlan |
| physical_network | physnet_bo-az3 |
| segmentation_id | 1115 |
+------------------+--------------------------------------+

$ openstack subnet create --no-dhcp --network private-provider-trust --network-segment private-provider-trust-az4 --ip-version 4 --allocation-pool start=10.52.172.14,end=10.52.172.235 --subnet-range 10.52.172.0/22 --dns-nameserver 10.10.10.10 --gateway 10.52.172.1 private-provider-trust-az4-subnet
+----------------------+------------------------------------------------------+
| Field | Value |
+----------------------+------------------------------------------------------+
| allocation_pools | 10.52.172.10-10.52.172.245 |
| cidr | 10.52.172.0/22 |
| created_at | 2022-03-31T19:26:48Z |
| description | |
| dns_nameservers | 10.10.10.10 |
| dns_publish_fixed_ip | None |
| enable_dhcp | False |
| gateway_ip | 10.52.172.1 |
| host_routes | destination='10.52.160.0/22', gateway='10.52.172.1' |
| | destination='10.52.164.0/22', gateway='10.52.172.1' |
| | destination='10.52.168.0/22', gateway='10.52.172.1' |
| id | 04a15cdd-d22b-4e58-8bbd-8b956d8c10ba |
| ip_version | 4 |
| ipv6_address_mode | None |
| ipv6_ra_mode | None |
| name | private-provider-trust-az4-subnet |
| network_id | ac30a487-bccc-4ac5-93eb-c422ad9f3ce5 |
| prefix_length | None |
| project_id | 561e8d2236634ece81ffa22203e80dc7 |
| revision_number | 0 |
| segment_id | 92355e6d-a5de-4b29-a956-1b05c4c9a33e |
| service_types | |
| subnetpool_id | None |
| tags | |
| updated_at | 2022-03-31T19:26:48Z |
+----------------------+------------------------------------------------------+

If I create the 4th subnet without specifying a gateway, then the routes are not created. It looks like this may be what changed from Queens to Train:

$ openstack subnet create --no-dhcp --network private-provider-trust --network-segment private-provider-trust-az4 --ip-version 4 --allocation-pool start=10.52.172.10,end=10.52.172.245 --subnet-range 10.52.172.0/22 --dns-nameserver 10.10.10.10 private-provider-trust-az4-subnet
+----------------------+--------------------------------------+
| Field | Value |
+----------------------+--------------------------------------+
| allocation_pools | 10.52.172.10-10.52.172.245 |
| cidr | 10.52.172.0/22 |
| created_at | 2022-03-31T20:00:44Z |
| description | |
| dns_nameservers | 10.10.10.10 |
| dns_publish_fixed_ip | None |
| enable_dhcp | False |
| gateway_ip | 10.52.172.1 |
| host_routes | |
| id | 11757c89-2057-4c7c-9730-9b7d976e361e |
| ip_version | 4 |
| ipv6_address_mode | None |
| ipv6_ra_mode | None |
| name | private-provider-trust-az4-subnet |
| network_id | ac30a487-bccc-4ac5-93eb-c422ad9f3ce5 |
| prefix_length | None |
| project_id | 561e8d2236634ece81ffa22203e80dc7 |
| revision_number | 0 |
| segment_id | 92355e6d-a5de-4b29-a956-1b05c4c9a33e |
| service_types | |
| subnetpool_id | None |
| tags | |
| updated_at | 2022-03-31T20:00:44Z |
+----------------------+--------------------------------------+
On Wednesday, March 30, 2022, 09:01:23 PM EDT, Brian Haley <haleyb.dev@gmail.com> wrote:


Hi,

On 3/30/22 15:27, Albert Braden wrote:
> The command that we use to create subnets looks like this:
>
> openstack subnet create --no-dhcp --network trust --network-segment
> trust-az1-seg --ip-version 4 --allocation-pool
> start=10.52.160.14,end=10.52.160.235 --subnet-range 10.52.160.0/24
> --dns-nameserver 10.10.10.10 --gateway 10.52.160.1 trust-az1

Since you're not specifying --host-route there should be none, can you
paste the created object returned from this call since for me
host_routes is blank (see below).

> My co-workers tell me that we also specified "--gateway" when we created
> our Queens subnets, but this did not cause static routes to be created.
> Did the handling of "--gateway" change from Queens to Train?

I don't believe so, and --gateway will default to the first IP in the
subnet if not given so isn't required.

-Brian


$ openstack subnet create --subnet-pool
f5e3f133-a932-4adc-9592-0b525aec278f --network private private-subnet-2
+----------------------+---------------------------+
| Field                | Value                    |
+----------------------+---------------------------+
| allocation_pools    | 10.0.0.66-10.0.0.126      |
| cidr                | 10.0.0.64/26              |
| created_at          | 2022-03-30T17:38:40Z      |
| description          |                          |
| dns_nameservers      |                          |
| dns_publish_fixed_ip | None                      |
| enable_dhcp          | True                      |
| gateway_ip          | 10.0.0.65                |
| host_routes          |                          |
| id                  | ce09a038-b918-4208-9a3d-c8c259ae7433 |
| ip_version          | 4                        |
| ipv6_address_mode    | None                      |
| ipv6_ra_mode        | None                      |
| name                | private-subnet-2          |
| network_id          | baf6c62d-4cec-464e-a768-253074df8879 |
| project_id          | 657e6d647c0446438c1f06da70d79bed |
| revision_number      | 0                        |
        | segment_id          | None                      |

| service_types        |                          |
| subnetpool_id        | f5e3f133-a932-4adc-9592-0b525aec278f |
| tags                |                          |
| updated_at          | 2022-03-30T17:38:40Z      |

+----------------------+---------------------------+

> On Wednesday, March 30, 2022, 01:45:52 PM EDT, Brian Haley
> <haleyb.dev@gmail.com> wrote:
>
>
> Hi Albert,
>
> On 3/29/22 17:04, Albert Braden wrote:
>  > After upgrading our kolla-ansible clusters from Queens to Train, we
> are seeing static routes when we create subnets. We didn’t see this in
> Queens. For example, in our de6 region we have a network called “trust”
> with 3 subnets:
>  >
>  > Subnet                CIDR                                  Gateway
>  > trust-az1:            10.52.160.0/22  10.52.160.1
>  > trust-az2:            10.52.164.0/22  10.52.164.1
>  > trust-az3:            10.52.168.0/22  10.52.168.1
>  >
>  > Each of these subnets has 2 entries under “host_routes:” that point
> to the other two subnets. For example, subnet trust-az1 has these two
> routes:
>  >
>  > host_routes          | destination='10.52.164.0/22',
> gateway='10.52.160.1' |
>  > |                      | destination='10.52.168.0/22',
> gateway='10.52.160.1' |
>  >
>  > How can we prevent these host routes from being created in Train? Do
> we need to change something in our config?
>
>
>  From the neutron side of things, host_routes of a subnet is not
> automatically calculated and filled-in, they have to be manually added.
> So perhaps this is something kolla is doing? At least on my Yoga setup
> it is completely blank using 'openstack subnet create ...' even with
> multiple subnets on a network.
>
> How exactly are the subnets getting created?
>
> -Brian
>