Receive/Transmit

This is going to be a series of short posts on little features in IOS which make your life easier. These won’t change your life or anything, but knowing them will make you much more proficient when sitting at a console. The first feature I’m going to discuss I hope everyone is aware of, the command lookup. This is incredibly useful when you can’t quite remember what command you need and it can be used in two slightly different ways.

The first way is when you have no clue at all what you need to type, and just want a refresher of what options are available. Typing the ‘?’ character will show you all possible commands with a brief description, eg

Router#?
Exec commands:
 <1-99>           Session number to resume
 access-enable    Create a temporary Access-List entry
 access-profile   Apply user-profile to interface
 access-template  Create a temporary Access-List entry
 archive          manage archive files
 audio-prompt     load ivr prompt
 auto             Exec level Automation
 beep             Blocks Extensible Exchange Protocol commands
 bfe              For manual emergency modes setting
 calendar         Manage the hardware calendar
 call             Voice call
 ccm-manager      Call Manager Application exec commands
 cd               Change current directory
 cellular         cellular commands
 clear            Reset functions
 clock            Manage the system clock
 cns              CNS agents
 configure        Enter configuration mode
 connect          Open a terminal connection
 copy             Copy from one file to another
 credential       load the credential info from file system
 crypto           Encryption related commands.
 --More--

Press space to see more. You can also use this on a nested basis, eg

Router#show access-lists ?
 <1-2799>    ACL number
 WORD        ACL name
 compiled    Compiled access-list statistics
 rate-limit  Show rate-limit access lists
 |           Output modifiers
 <cr>

Router#show access-lists

The second, slightly different way to use this is when halfway through a command, it will try and match based on what you have already typed

Router#show ip in?
inspect  interface

Router#show ip i?
icmp  igmp  inspect  interface
ips   irdp

Router#show ip in?
inspect  interface

Router#show ip in

However note that in this case you don’t get the command descriptions.

You can use this from any mode, so it works in config, user exec, privileged exec. A lot of the commands you’ll come to learn by heart, but this is very useful for the ones you use less often.