MTU is a new read-only attribute for neutron net,
This should be displayed back in the attributes.
localadmin@devstack:~/devstack$ neutron net-create test
Created a new network:
+---------------------------+--------------------------------------+
| Field | Value |
+---------------------------+--------------------------------------+
| admin_state_up | True |
| id | adf09ab3-6242-4d27-ba0e-b0130cb5a900 |
| mtu | 1500 |
| name | test |
| provider:network_type | vlan |
| provider:physical_network | physnet1 |
| provider:segmentation_id | 392 |
| router:external | False |
| shared | False |
| status | ACTIVE |
| subnets | |
| tenant_id | d670408526c24224977d1de6953f700b |
| vlan_transparent | False |
+---------------------------+--------------------------------------+
localadmin@devstack:~/devstack$
As a short-term workaround, this could be specified via extra_specs