When enabled on a virtual terminal, logging synchronous causes all router status messages to be displayed on a new line.
For this example, logging synchronous was disabled for vty 1 on R2.
R2(config-line)#no logging synchronous
Notice now that, when status messages are displayed, they display on the current line. This means that if you are in the middle of typing a command, status messages will show up where you are typing.
R2(config)#int loopback *Mar 1 00:37:55.987: %LINK-5-CHANGED: Interface Loopback99, changed state to administratively down *Mar 1 00:37:56.987: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback99, changed state to down99
In the text above, the command that we were trying to type was int loopback 99. This got cut off by the status message that was displayed on the same line.