How to connect a host inside Containernet to a VM outside it (but still in one PC)?

Question

I have the following configurations:

1. Inside one PC, I have 3 VMs as follows: VM-1 has Containernet, VM-2 has ONOS Controller, and VM-3 is standard Ubuntu 20.04. Naturally, these 3 VMs can ping each other.
2. I successfully ran the Containernet and used the ONOS as the remote controller. Inside the Containernet there are 1 Switch and 2 Hosts. These 2 Hosts can ping each other and I can see the topology from ONOS Web GUI

However, from the host inside the Containernet, I cannot ping the host PC and VM-3 (and vice versa). Any solution for this?

I have tried the following possible solutions found on the Internet but to no avail:

1. Make sure that the interface connected to the Containernet network is configured with the correct IP address and subnet mask
2. Set up routing rules to ensure that traffic can flow between the two networks

I appreciate any help.

Thanks and cheers,