Control Console and Terminal Logging in Cisco Router and Switches
You might have experienced that while you are typing a command on a terminal, some stuff get thrown to the terminal by the router or the switch making it a mess. This stuff can be useful specially when you are configuring a routing protocol or changing setting on an interface. However messages like the following, is quite disturbing when you are doing some task.
1 2 3 4 5 6 7 8 9 | Router(config)# Router#show *Mar 1 00:07:23.487: %SYS-5-CONFIG_I: Configured from console by consolerun Building configuration... Current configuration : 694 bytes ! version 12.3 |
Above terminal output is a good example. A message has been thrown in between me “show run” command. The router understood the command perfectly, but it we cat read it clearly. The reason for this is logging. Routers and switches use console ports to log messages. You can three options to stop or minimize the logging disturbances on terminals.
Disable Logging Completely
This method is quite straight forward and you’ll loose the ability to see what’s going on in the router while you are configuring. You might want to know when a network interface goes up or down, neighbor relationship formation, etc. So this is the least useful method, but you do not get any messages on your console.
1 | Router(config)#no logging consol |
Configure Logging Levels
Cisco routers, switches, PIX and ASA firewalls prioritize log messages into 8 levels.
1 2 3 4 5 6 7 8 9 | Level Level Name Description 0 Emergencies System is unusable 1 Alerts Immediate action needed 2 Critical Critical conditions 3 Errors Error conditions 4 Warnings Warning conditions 5 Notifications Informational messages 6 Informational Normal but significant conditions 7 Debugging Debugging messages |
Log messages with lower numbers are more critical than higher numbers. If you specify a level, let say Warnings all the messages belong to that level and above (lower numbers) are logged for you.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | Router(config)#logging console ? <0-7> Logging severity level alerts Immediate action needed (severity=1) critical Critical conditions (severity=2) debugging Debugging messages (severity=7) emergencies System is unusable (severity=0) errors Error conditions (severity=3) guaranteed Guarantee console messages informational Informational messages (severity=6) notifications Normal but significant conditions (severity=5) warnings Warning conditions (severity=4) xml Enable logging in XML Router(config)#logging console |
You can either specify the number or the name of the level. Here I have configured it to show me warning on the console.
1 | Router(config)#logging console warnings |
This does the same as the above command. Router(config)#logging console 4 You can do the same for VTY terminals. Use logging monitor instead of logging console in global configuration mode.
1 2 3 4 5 6 7 8 9 10 11 | Router(config)#logging monitor ? <0-7> Logging severity level alerts Immediate action needed (severity=1) critical Critical conditions (severity=2) debugging Debugging messages (severity=7) emergencies System is unusable (severity=0) errors Error conditions (severity=3) informational Informational messages (severity=6) notifications Normal but significant conditions (severity=5) warnings Warning conditions (severity=4) xml Enable logging in XML |
Logging Synchronous
In Synchronous logging, after the message is thrown in to the terminal, router displays the original prompt with what you have already typed. To enable synchronous logging on console ports:
1 2 3 4 | Router# Router#conf t Router(config)#line console 0 Router(config-line)#logging synchronous |
To enable logging synchronous on telnet terminals:
1 2 3 4 | Router# Router#conf t Router(config)#line vty 0 4 Router(config-line)#logging synchronous |
Now the out put is like this.
1 2 3 4 5 | Router(config)# Router#show run *Mar 1 01:44:37.067: %SYS-5-CONFIG_I: Configured from console by console Router#show run |
The router has repeated the prompt with that we have typed. You can get good results be combining the second and third methods wisely. Please see Cisco documentations for more on logging.
Dharshin
