By default, IOS displays syslog messages to the console users at any time, even during the typing of a command. Consider the following example:
R1(config-if)#ip address 192.168.0.100 255.2 %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down 55.255.0
Notice how the command was interrupted and the syslog message was shown. To prevent this, the logging synchronous console line mode command is used:
R1(config)#ip address 192.168.0.100 255.2 %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up R1(config)#ip address 192.168.0.100 255.2
Now, the syslog message was shown, but the command was copied to the next line below the message.
