When I connect to device with telnet or SSH I don't see logging?

Cisco device will not send log messages to your terminal session by default. That means that you will see log messages in putty only if you are connected to console port but if you connect with telnet or SSH you will not get log messages. Here’s how to resolve this:

There are three types of logging: Console, Monitor and Buffer.

Console logging is seen if you connect to console port directly. Monitor logging is what you will se on your screen when you are connected to CLi in some other way. And the last is Buffer logging that means all the logs that are going into buffer memory to be viewed later in time. Every of the logging type has its own setting on which loggs will be registered.

There are this types of looging levels with their severity numbers where greather number means smaller severity case, from severity 1 to 7:

 alerts         Immediate action needed              (severity=1)
 critical       Critical conditions                  (severity=2)
 errors         Error conditions                     (severity=3)
 warnings       Warning conditions                   (severity=4)
 notifications  Normal but significant conditions    (severity=5)
 informational  Informational messages               (severity=6)
 debugging      Debugging messages                   (severity=7)
 emergencies    System is unusable                   (severity=0)

If you want to se owerall logging settings for you device this is the way to check what logging settings you have on some cisco switch. Just type #show logging command.

SW#sh logging
Syslog logging: enabled (2466 messages dropped, 1 messages rate-limited, 2 flush                                                                                                                               es, 0 overruns, xml disabled, filtering disabled)

No Active Message Discriminator.

No Inactive Message Discriminator.

    Console logging: level notifications, 1093931 messages logged, xml disabled,
                     filtering disabled
    Monitor logging: level debugging, 10738 messages logged, xml disabled,
                     filtering disabled
    Buffer logging:  level warnings, 1004401 messages logged, xml disabled,
                     filtering disabled
    Exception Logging: size (4096 bytes)
    Count and timestamp logging messages: disabled
    File logging: disabled
    Persistent logging: disabled

Turn logging ON

If you want to configure logging so that it shows in your terminal the #terminal monitor command will help you acoplish that.

s1#term mon

That’s all you have to do. Logging to your terminal will now be sent and you will be able to see it. If nothing is going on on that switch you will of course not see anything. If you want to check if the logging is working on of the things you can do is to shutdown and interface and bring it back up. Then you will see some logging going on.
If there is a word about production device and you can not simply bring interfaces on and off the step to take is #show logging command again.
If your #terminal monitor command was sucesfully applied you will see that for your terminal session you have logging enabled. Here is this example you will see that the Logging to: vty1(0) appeared. That is your proof when you see that a terminal session is mentioned under Monitor logging part of status.
SW#sh logg
Syslog logging: enabled (2466 messages dropped, 1 messages rate-limited, 2 flushes, 0 overruns, xml disabled, filtering disabled)

No Active Message Discriminator.

No Inactive Message Discriminator.

Console logging: level notifications, 1094000 messages logged, xml disabled,
filtering disabled
Monitor logging: level debugging, 10756 messages logged, xml disabled,
filtering disabled
Logging to: vty1(0)
Buffer logging: level warnings, 1004468 messages logged, xml disabled,
filtering disabled
Exception Logging: size (4096 bytes)
Count and timestamp logging messages: disabled
File logging: disabled
Persistent logging: disabled

No active filter modules.

......
Turning Terminal Logging OFF
s1#terminal no monitor
Confirm that Logging to: vty1(0) is realy my terminal:
Use show terminal to find out which line your on, and this is teh same number as the vty:
SW#sh terminal
Line 1, Location: "", Type: "xterm"
Length: 24 lines, Width: 80 columns
Baud rate (TX/RX) is 9600/9600
In this case there is Line 1 mentioned int he first row and that means you’re on vty1.