I saw a (possibly) similar problem with my setup wen running earlier builds of LMCE. In that case, the internal ethernet adapter on the server stopped letting traffic through, even though ifconfig and ethtool showed a working adapter. I couldn't even ping the hybrid core from the internal network This only happened when I had MDs on the internal network. If I shut those down, I never saw this problem. Nothing else (switches, cabling, etc) seemed to affect the issue. It seems to have disappeared with 0810. Do you see this issue if you have no MDs on the system (i.e. standard windows or linux PCs)?