Disable console logging

Large amount of logging output (most often produced in a debugging process) sent to a router's console can significantly increase the router's CPU load and even stop the box from forwarding packets (high-end routers with distributed forwarding architecture are obviously an exception, but even they can lose routing adjacencies). The reason is very simple - console interrupt is one of the highest-priority interrupts on the router (otherwise you wouldn't be able to get a response to the BREAK key on a hung box).

Update January 9th 2007: The router does not check if a user is logged into the console port or a device (for example, a terminal) is attached to it; if console logging is enabled, messages are always sent to the console port (causing CPU load).

To stop the console logging, use the no logging console global configuration command (highly recommended for routers that are not usually accessed through the console port) or you might want to limit the amount of messages sent to the console with the logging console level configuration command (for example, logging console notifications).

Note: this article is part of You've asked for it series.

8 comments:

  1. Does the router's CPU get taxed by console logging even if no one is logged into it?

    ReplyDelete
  2. Hi
    I have a 2612 Cisco router
    the console port not any things shown in hyper, But another router is show console and etc...
    means my console cable and hyper is OK
    in router aux is active but not set pass, so i don't access to enable privilege
    please help me :'(

    ReplyDelete
  3. I think to completely disabled console port on Cisco router for some security reason.


    can anyone tell me how can i cancel this ?
    also not set pass in aux port and admin shut in Fast Ethernet on router
    plz help meeeeeeeeeee *DONT_KNOW*

    ReplyDelete
  4. sir, i have a cisco router with console port disabled. how i can access the router through this console port. or how i can set it again to utilize for accessing the router........ plz answer me on my email thanks
    liaqat_buneri@yahoo.com

    ReplyDelete
  5. There is a possibility to configure "logging rate-limit console" to limit the rate of messages thrown to console, along with the optional "except" keyword makes a usable trade-off.

    ReplyDelete
  6. switch(config)#line consol 0
    switch(config-line)#no exec

    ReplyDelete

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Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.