How to solve the problem when the serial physic signal is not completely up?
1, Check whether the router and DCE equipment interface type is consistent. After insuring the consistent of the interface type, the link is normal, and then the show interface will examine the physic signal condition; if some signals condition is down in DCE, DSR, CTS, TXC, it means the DCE equipment has some problem. If TDR, RTS signal condition is down, it means the router have some problems, check whether the interface configuration has done the shut down operation, if not, the problem may be in the module or router slot. So first displace serial module, and then the slot to solve the problem.
