AFAIK, If you set VM DC1 to use a VirtualBox network card Bridged to eth0, and set the a static IP (10.0.11.1/24) in the VM, then eth0 on the host will be listening on 192.168.1.150/24 (for the host) AND on 10.0.11.1/24 (for the guest DC1).
Whether another real PC on the actual network can connect to 10.0.11.1/24 listening on eth0 is another matter, subnets and all that.
Likewise VM DC2 can use a VirtualBox bridged connection to eth1 which will have IPs 192.168.1.151/24 (host) and 10.0.11.2/24 (DC2) on the host's eth1.
Debian VM3 could have have 192.168.1.152/24 (host), 10.0.11.3/24 (VM eth0?) and 172.104.xxx.xxx (VM eth1?) all on host eth2.
You might also investigate : VDE (Virtual Distributed Ethernet) networking.
(One paragraph in the manual: http://www.virtualbox.org/manual/ch06.html
... refers you to the VDE website.)
That might simplify things a lot (or not).