The status of the physical links of the AR router cannot turn Up after PPP or MP is configured on the router.
View the current status of the interface by running the display interface type number command.
The interface may be in one of the following states:
serial number is administratively down, line protocol is Down:
It indicates that the interface is shut down by the administrator. In this case, run the undo shutdown command to enable the interface.
serial number is Down, line protocol is Down:
It indicates that the interface is not activated or the physical layer is not resumed to the Up state. In this case, troubleshoot the lines to check whether the parameters of the interfaces at both ends match each other.
Virtual-template number is Down, line protocol is spoofing up:
It indicates that the interface is a dialer port and the caller is not put through, which is normal. When the dial-up connection is established, the status of the interface turns Up.
serial number is Up, line protocol is Up:
It indicates that the link negotiation, namely, LCP negotiation, of the interface succeeded.
serial number is Up, line protocol is Down:
It indicates that the interface is activated, but the link negotiation failed. In this case, check the configurations of PAP and CHAP authentication.