I am running eNSP (.370) in one of my machine, testing my design using 6 routers and 4 switches, it works fine initally but certainly i can see one interface is physically up but line protocol is down, I have restarted both the routers in order to get that interface up. It works fine for sometime. But after sometime interface of other router went down and then I have to reboot that router to get the interface up and so on.