Category: EEM

The IOS command line interface has long included unix-style pipes that you could use to limit the output generated by the show commmands. Initially, the only available filters were begin (include everything after the first regular expression match), end (stop the output at the RE match) or include (include only matching lines).

IOS release 12.3(2)T (integrated in 12.4) brought us a few new filters, among them the section filter that includes or excludes whole sections (start of section being defined by a line with no leading space). You can use this filter to focus on parts of your router configuration. For example, to display only the routing protocols configuration, use show running | section include router command.

Embedded Event Manager is a bit picky about the location of the EEM Tcl policies: although they are loaded into RAM when registered, they have to reside on the router itself. If you have a low-end router with no flash disk (I'm using 2800-series routers) or USB flash and you don't want to mess with your flash: device (to prevent accidental erasure), the only other place left is NVRAM:. Surprisingly, it works.

The IP Service Level Agreement (SLA) measurement feature of Cisco IOS is extremely SNMP-oriented. For example, there is no easy way to generate a logging message when an SLA operation fails (or exceeds the threshold). However, Embedded Event Manager reading SNMP variables can help you get there.

Have you ever wanted to be notified when your router loses a specific route (for example, the default route toward the Internet)? In IOS release 12.4T you can do it with a combination of Enhanced Object Tracking and Embedded Event Manager 2.2.

I've tried to be a "good citizen" in one of my Embedded Eveng Manager (EEM) applications and used the action 1.1 cli command "copy running-config startup-config" instead of the (supposedly obsolete) action 1.1 cli command "write memory" command. However, as the copy command generates console prompts (unless you turn them off with the file prompt quiet command), it immediately hung my EEM applet.

Moral of the story: use write memory :)

The Cisco IOS’s AAA architecture contains many handy features, including authorizing and logging every CLI command executed on the router. Unfortunately, the AAA command accounting only supports TACACS+ as the AAA transport protocol, making it unusable in RADIUS environments.

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

Sometimes when using not-so-very stable IOS versions, periodic reload of a router during a non-peak (or idle) period is a good idea that can significantly increase the overall stability of your network. Until release 12.4, you had to write an external script that would log into the router and execute the reload command.

With the Embedded Event Manager, the task is surprisingly simple - just enter the following configuration commands to reload the box every midnight (of course it helps if your router is NTP-synchronized to a reliable clock source and has correctly configured time zone).