Symptoms:
Trying to attach a L2VPN Stretched Logical Switch to a Logical Router, it fails with the following error
VMware NSX-T Data Center
VMware NSX-T Data Center 2.x
This behavior is expected. In NSX-T 2.3 and all the prior versions you cannot have a L2VPN stretched and routed at the same time.
Starting NSX-T 2.4, a feature has been added that to attach a L2VPN Stretched Logical Segment to a Logical Router to configure routing on a stretched L2 network.