The logging userinfo configuration command introduced in IOS release 12.3T (integrated into 12.4) starts logging of all changes in user privilege levels (as requested by enable or disable commands).

When I was still teaching Cisco courses, we were telling the students that the order of network statements in an OSPF process was important if their ranges were overlapping; the first network statement that matched an interface IP address would place that interface in the corresponding area. This is no longer true, Cisco IOS now properly handles overlapping network ... area configuration commands.

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You can preview this digital book (they call it Digital Short Cut) using the Safari technology at Cisco Press and buy it at Amazon.

I always hate it when Cisco IOS asks me for things I've already supplied in a command line, the most notable case being the copy command. For example, if you supply the complete source and destination file name in the command line, IOS still insists on asking you all the same questions (at least filling in the parameters I've supplied in the command line):

fw#copy system:running-config tftp://10.0.0.2/fw-test
Source filename [running-config]?
Address or name of remote host [10.0.0.2]?
Destination filename [fw-test]?
!!
2009 bytes copied in 0.604 secs (3326 bytes/sec)

You can disable the annoying questions with the file prompt quiet configuration command (the default value of this parameter is noisy).

As part of Configuraton Change Notification and Logging feature, Cisco IOS stores the most recent configuration commands in a circular buffer and (optionally) sends them to syslog streams.

This feature is configured under the archive configuration mode with the log config command, which brings you to yet another configuration mode where you can fine-tune the parameters (they are obvious, on-router help is sufficient), for example:

archive
 log config
  logging enable 100
  notify syslog
  hidekeys

After you've enabled configuration command logging, you can use the show archive log config all command to inspect the logging buffer. You can also display commands entered in a particular session or by a selected user.

If you've configured notify syslog, every configuration command also triggers a syslog message similar to this one:

3d03h: %PARSER-5-CFGLOG_LOGGEDCMD: User:console logged command:interface loopback 0

Note: This feature logs only the configuration commands, if you want to log all commands, use TACACS+ or Embedded Event Manager.

The AAA architecture of Cisco IOS contains a number of very useful features, including the ability to authorize and log every CLI command executed on the router. Unfortunately, the AAA command accounting only supports TACACS+ as the AAA transport protocol, making it unusable in environments using RADIUS.

You can use Embedded Event Manager as a workaround. The following configuration commands will log every command executed on the router.

event manager applet CLIaccounting
event cli pattern ".*" sync no skip no
action 1.0 syslog priority informational msg "$_cli_msg"
set 2.0 _exit_status 1

The log messages generated by this EEM applet have the following format:

%HA_EM-6-LOG: CLIaccounting: command

As the EEM uses standard IOS logging mechanisms, you can use the show logging command to examine the command execution history or store the messages on a syslog server.

Note: As a side effect, all commands executed on a router will be echoed to the router's console, unless you disable console logging with no logging console command or use TCL-based syslog filters (more about them in an upcoming post).

In the article Perfect Load-Balancing: How Close Can You Get?, you'll find in-depth information on how you can use MPLS traffic engineering to load-balance traffic in highly redundant designs.