I am running with 4 core switches of 6509 with fibre connectivity having two different sites. Each site is having two core routers.One site ( A ) does have CISCO IOS version and does not have any problem but other side (B) running with CAT-os has huge problem. Suddenly the whole site got down for a minute or two and then it come normal. It happens in not a specific time, Just random. Can any one give me any suggestion to find the problem or resolve the issue.