Welcome to the Community,
do you use a wired or wireless network adapter on the host? In case you have multiple network adapters in the host, open the "Virtual Network Editor" and specify the active network adapter for the Bridged Network "rather then using "Automatic".
Are the host and the guest configured to receive their IP settings from DHCP or do they use fixed settings (e.g. duplicate IP addresses)?
What type of switch/router is the host connected to?
André