Concept of bridge networking


I have question about Bridged Networking with Security Group

Versions: 5.4.6

I have created two virtual networks with Security Group. They are binding to the same physical bridge interface with different IP address arrangement but same subnet.

They have configed to different VM template.

2 VMs built up and its belongs to two different users. However, they can communicate to each others.

I want to isolate them using Bridged with Security Group. But it is fail now. Where is my setting goes wrong? or I should using 802.1Q network with different VLAN setting?