VertexAI notebook does not obtain Shared VPC IP

[dgnemo]

Hello, 

when I create a new VertexAI notebook I can select:

networking:  Shared network (from host project: XXXC) 

GCP then asks me the network and the subnet.
In the subnet dropdown the tooltip reads:

Assigns the notebook an IPv4 address from the subnetwork's range. Notebooks in different subnetworks can communicate with each other using their internal IPs as long as they belong to the same network.

But this does not seem to work at all ?

Once I create the notebook I can run ifconfig in the terminal and there it's clear that the notebook never got an IP from the subnet I selected above.

Anyone knows how I can use this feature?
Thanks!