The configuration register can be used to change router behavior in several ways, such as: how the router boots (into ROMmon, NetBoot) options while booting (ignore configuration, disable boot messages) console speed (baud rate for a terminal emulation session) To view the current setting of the configuration register, use the show version command:

In a network environment, it is a good practice monitor Cisco devices. One of the most famous protocol to control and manage Cisco devices is SNMP (Simple Network Management Protocol). SNMP exposes management data in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications. The main features are: The SNMP is an application layer protocol that facilitates the exchange of management information between network devices. It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. It uses UDP port 161 for the [...]

Due to the number of CLI commands needed to manually disable services in an attempt to make the router more secure, Cisco introduced the AutoSecure feature from the Major Release 12.3 and subsequent 12.3 T. AutoSecure is a good command for customers without special Security Operations Applications because it allows them to quickly secure their network without thorough knowledge of all the Cisco IOS features. The command is available for the Cisco 800, 1700, 2600, 3600, 3700, 7200, and 7500 Series Routers. There are 2 mode: Interactive mode: prompts the user with options to enable and disable services and other [...]

The Cisco DHCP server feature is a full implementation that assigns and manages IP addresses from specified address pools to DHCP clients. After a DHCP client has booted, the client begins sending packets to its default router. The IP address of the default router should be on the same subnet as the client.

When you read official documentation from cisco.com, there are some conventions that is opportune to know. Some examples of Cisco conventions: * Bold indicates text the user must enter or select, such as menu items, buttons, and commands.

Surfing the web, I have found a document concerning the undocumented cisco commands. The document is write by Lars Fenneberg (CCIE #7325) and it’s quite old (last revision in 2005). Certainly this is not a complete list, but I suppose that could be funny to discover some new commands… I have tried to found other document more exhaustive with no result.