By default, Cisco IOS displays syslog messages to the console users at any time, even while typing a command in the config line. 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 by the syslog message. To prevent this, the logging synchronous Cisco 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
The syslog message was shown, but the command was copied to the next line below the message. The logging synchronous command also synchronize unsolicited messages, log messages, and debug output with the solicited user input and prompts.
There are optional keywords that can also be specified, such as the message severity level and the number of buffer limit.
logging synchronous [level [severity-level | all] | limit number-of-buffers]
To disable synchronization, use the ‘no’ form of the logging synchronous Cisco command:
no logging synchronous
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