From: James Ventre (messageboard@ventrefamily.com)
Date: Sat May 20 2006 - 12:12:04 ART
logging sync may be appropriate in the lab, but it's a terrible idea on
production devices (on the console). Because console logging is such a
high priority (and because it operates at the interrupt level) it can
cause excessive cpu utilization. Typically you know you have this
problem when the TTY Background process is unusually high. A number of
the cisco best practices documents specifically warn against this.
http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a00801c2af6.shtml
TTY Background
The TTY Background process is a generic process used by all terminal
lines (console, aux, async, and so on). Normally there should not be any
impact on the performance of the router since this process has a lower
priority compared to the other processes that need to be scheduled by
the Cisco IOS software.
If this process takes high CPU utilization, check whether "logging
synchronous" is configured under "line con 0". One possible cause could
be CSCdy01705 (registered customers only) .
James
darbyweaver@yahoo.com wrote:
> I just use:
>
> conf t
> line con 0
> logg sync
>
> Then if I am getting messages they don't interrupt my line of thought or my commands.
>
> Under each routing process, such as BGP, OSPF, and EIGRP, you have the option to turn on or turn off logging as well - which may alleviate some of the error messages you are experiencing. Also under the command logging you can change the variables as to what messages you will see as well.
>
> So you have a few options available.
>
> Others may know more or more refined techniques.
>
> I personally like seeing the logs and anticipate them, and then just work around them.
>
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