This depands on what cyrptographic standards are required by the military application. For most highly classified applications the military requires its own non-commercial "type-1" cryptography to be used. There are specialist companies looking at in...
Line protocol down means that the router cannot see "keepalive" packets from a router at the other end of the serial link. This might be because the encapsulation configured on the routers at each end of the serial link is different, eg. one end "enc...