klaus999 wrote:
Details:
VMWare WS 8.0.6 build-1035888
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I did not had any problems over 3 years. The config has not changed in the VMsystem
You may not have had problems for over 3 years however things have changed because you say you're using VMware Workstation 8.0.6 and that was released on 03-14-2013 so obviously things have changed over the years! 
What was the original version the VM's were created in? Probably some version of VMware Workstation 7.x and how many times did you update/upgrade WS and updated VMware Tools? So changes have been made to virtual hardware version and VMware Tools and Guest OS updates over the years! BTW No real need to answer these questions I've asked because it was just to put in perspective that things have indeed changed!
Since this behavior has started recently is it safe to assume that it started after the VMware Workstation 8.0.6 update? There may be a bug in it that's causing this issue. Anyway you'll need to manually release the DHCP IP Addresses in the Router if they are not aging out as they should. Also it might be something wrong with your Router and I'd check to see if there are and Firmware updates for it.