“I’m a little confused on what the “show controllers” commands really do… can someone clarify? Based on the output, I’m inclined to suspect that it provides mostly physical layer type information about an interface. From a troubleshooting perspective, when is it useful to use this command? Looks like it’s great for verifying DTE / DCE cabling inputs… what else?” —From learningnetwork.cisco.com
The show controllers command is used to display controller information (primarily diagnostic, driver level details) for an interface. The information displayed varies widely by interface type and is extremely hardware specific.
Many of the fields displayed (e.g. CSRn, etc.) are driver control and status registers. .
For a serial interface, the output of this command will show you whether a DTE (Data Terminal Equipment) or a DCE (Data Communication Equipment) cable is connected to the interface. In a production environment, the router is typically the DTE and the modem or CSU/DSU (channel service unit/data service unit) is the DCE. The DCE end always provides the clocking for a synchronous serial link.
For additional show controllers syntax, type in show controllers?. This will provide available syntax.
Example of the show controllers on Cisco 7206VXR:
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