Topic Name : Create an External Network with NSX-T Networking
Publication Name : VMware Integrated OpenStack Administration Guide
Product/Version : VMware Integrated OpenStack/5.1
"Select External from the drop-down menu." It should be; "Select Local from the drop-down menu to connect future Tenants Logical Routers (Tier-1) on default Tier-0. If you want to connect future Tenants Logical Routers (Tier-1) on other Tier-0, do xxx (see "New Testament" - if you don't know ask firstname.lastname@example.org where is that doc).