There are many commands that are usable on Cisco routers that can not be found in the documentation, or with the ?. Here is a list of some of these commands

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aaa accounting delay-start
[12.1] [hidden] global configuration command aaa accounting delay-start delays creation of the PPP Network start record until the peer IP address is known. 

aaa authorization address-authorization-exec
[12.1] [hidden] configuration command forces address authorzation for PPP when started from an exec. 

aaa group server {radius | tacacs+} server-group-name server (ip-address-1) [auth-port (port-number)] [acct-port (port-number)] server (ip-address-2) [auth-port (port-number)] [acct-port port-number] deadtime (minutes) pick-method [next | load-balanced | round-robin]
[hidden] Pick-method server-group configuration command used to specify an alternate method of selecting servers when one is not responding. As of 12.0(3)T the load-balanced and round-robin alternatives may be specified butmay not be implemented. The load-balanced keyword indicates that the initial host is selected load-balanced. The round-robin keyword indicates that the initial host is selected in a round-robin method with all servers being retried before starting from the beginning of the list of servers. The next keyword indicates that the list of servers is stepped through sequentially with each request always starting with the first server in the list. This last option is the default method of operation. 

aaa nas port description text
[hidden] global configuration command causes the specified text to appear in TACACS+ accounting records with the attribute nas-description and the value of the text specified in the command. This command is useful during debugging allowing one to specify information about the environment or configuration in which the accounting record was generated. 

access-list number remark (comment)
and
ip access-list extended name remark (comment)
[12.1] Option to add comments about the access list. This keyword is documented under Bug Id CSCdk14543. 

Introduction

There is a significant increase in the number of companies choosing to deploy Cisco Unified Communications when phasing out their traditional time division multiplexed (TDM) based systems. Security is now one of the highest selection criteria for IT professionals, becoming as important as the features the system offers, when selecting the new system. Unified Communications is not dedicated to its own cable infrastructure as the traditional PBX systems were, but rather uses a shared IP based infrastructure. Voice over Internet Protocol (VoIP) defines a way to carry voice calls over an IP network including the digitization and packetization of the voice streams. Voice traffic travels along with the data traffic over the same IP network. All of the same security technologies and policies deployed to protect the data network can be used to protect the voice service as well.