I have a large LAN at my company. I suspect that there is a failure of a router or of a transmission line connecting routers. I want to narrow down the search, where is the fault. How could I narrow down the location of the problem.
Why do you think that there is a failure in your network? If some hosts are unreachable than
If you want to hear a general advice, then I would recommend to find or make a detailed network scheme for a start.
BTW you should think about installing at least a basic NMS to be able to manage a large LAN. Consider for example free and opensource Nagios.