We currently use VDX for layer 2 switching only, and we are hoping to use them for some layer 3 routing.
According to the documentation once the command "router fabric -virtual-gateway" is enabled, Vlan interfaces need to be attached to rbridges as described below:
device(config)# interface ve 2000
device(config-Ve-2000)# attach rbridge-id add 54,55
Then the fabric gateway is enabled and ip address applied:
device(config-Ve-2000)# ip fabric-virtual-gateway
device(config-ip-fabric-virtual-gw)# gateway-address 18.104.22.168/24
Since vlans are create for layer 2 operation by creating them as interfaces, my concern is that layer2 switching will be interrupted after the router fabric-virtual-gateway is enabled until the attach command is issued, especially since this command is issued at the global ve command stanza, before the ip fabric-virtual-gateway is enabled.
Alas, I do not have a lab to test this, and will need to scale a maintenance window accordingly if layer 2 traffic is interrupted.