Cross coverage

what is requirement of cross coverage in SystemVerilog?

In reply to Mukund Sojitra:

Cross coverage is just one way of measuring the results of testing certain combinations of features. For example, if you have a router with 4 ports, you might want to test that each port sends and receives data. A cross would tell you that each port received data and sent it through every other port (12 possible combinations after eliminating the cases where receive and send happen on the same port).