Zend certified PHP/Magento developer

Virtualbox Cant ping VMs in same LAN

I have two hosts, with each of them running a single VM in VirtualBox, located in the same home LAN.
I have set bridged adapters for both VMs and the source IP address has the same subnet assigned as the destination IP address (source 192.168.18.15, destination 192.168.18.1).
When trying to pinging each other i get the response: Destination Host Unreachable.
In very rare random cases a connection is established but only for about 10 seconds before again getting the initial response.

see here

Pinging between hosts is possible. Any help is appreciated.