How to Change or Increase Cisco Router Logging

Cisco routers, as well as most other computer devices, have the ability to log messages about everything they do. These log messages are invaluable when trying to troubleshoot a really difficult network issue.

The problem with Cisco routers is that when you enable logging, the default size of the log is only 4096 bytes. With a log file this big it can typically only store about 60 messages. If your router is very busy these 60 messages will quickly scroll out of the buffer and be replaced by the next 60 messages of events going on with your router. This can get real frustrating, real quick.

To fix this you need to increase the size of your log file on your Cisco Router.

Increasing the log file will make it a whole lot easier to understand when and why things happen in your router. It’s an easy fix that you can do and will make your life much easier.

To double the log file you simple double the log size (in bytes). Here how you would increase your log file from 4096 bytes to 8192 bytes.

conf t
logging buffered 8192

Now that you’ve made the change, its a good idea to check the current log file size. Use this command to see your log file:

show logging
...
Log Buffer (8192 bytes)

One thing you need to keep in mind when increasing the size of your log is how much memory the router has to use for logging. Big routers have lots of memory however smaller router have much less memory and care should be taken when increasing your log file size.

For more logging then what is possible on the router itself  – try sending your logs to a remote syslog server!  This will allow for most of your log data to be stored in a long term archive.