Suddenly cannot connect from guest to hosts

[EnglishBulldog]

Hi,

I have a host and 2 guests. All running win 7.
Everything was fine for months and I was able to connect from all to all.
Recently, for no apparent reason and no setup change, I am only able to connect between the 2 guests but I'm unable to connect (ping) from the host to any of the guests.

[EnglishBulldog]

I found the cause to the problem and I want to share it. :
When ethernet cables is unplugged from pc, host cannot access guests.
When ethernet cables is connected to pc, host can access guests.
Issue closed.