Cisco IOS:
In this paper, you will learn how to use tools and commands built into Cisco's IOS to make configuring and monitoring your Cisco devices quicker and easier. We'll start with some basic, commonly used commands and settings. Then we'll move into more advanced ways to make your Cisco life easier, including some commands that are new with the most recent versions of the Cisco IOS. Topics covered include:
-Auto-completing commands - Disabling DNS server lookup - Limiting EXEC interruptions - Setting the console speed - Deprecated commands -Timestamping messages - Setting the clock and time zone - Displaying an interface config - Erasing an interface config - Filtering the output of commands - Do command -Alias commands - Privilege levels - Changing the TCPtimeout - Stopping runaway debugs - Editing access lists - Router autoconfiguration
Auto-Completing Commands
When typing a command, it is only necessary to type enough letters to make the command unique at your current configuration mode. Once you have enough letters that the Cisco IOS can understand what command you mean, you can stop typing. Type a few letters, then press the TAB key, if the router understands the command, it will complete it for you. If the router doesn't understand the command, type another letter or two, press TAB again, and see if that's enough. Typing fewer letters per command speeds-up your configuration, and creates fewer chances for typos!
Disabling DNS Server Lookup
When you type something (at the user or privileged prompt) that the router doesn't recognize as a command, it assumes that you want to telnet there. So it telnets there if it's an IP address, or looks in the config for a host table if you typed a word. If the word can't be resolved to an IP address via a host table, the router broadcasts for a DNS server. This is good if what you typed was an IP address or host name that you want to telnet to, it means you don't have to type the word telnet. This is bad if you just mistyped a command. It ties up the router until the DNS request times out. You can turn off the DNS request with the command no ip domain-lookup at the global config mode.
Limiting EXEC Interruptions
If the router has a message for you, it will display the message, even if that means interrupting something you were typing. Then you're stuck having to finish your command at the end of the router's message. The command logging synchronous under the console line configuration mode corrects this. The router still displays its message but will redisplay the command you were typing on the line when it's done. To turn off logging messages to the console altogether, give the command no logging console under global configuration mode. Note: This may cause you to miss some important messages from the router. You can modify this command by specifying the severity level of the message you want to turn off.
Setting the Console Speed
To connect via the console to a Cisco IOS device, your terminal emulation program needs to be set to the following specifications. (Later in this paper, we'll tell you how to change the console speed.) Baud rate: 9600 bps, Data bits: 8, Parity: None, Stop bits: 1, Flow control: None. These are the default settings for both the console and the auxiliary ports.
Although the console port defaults to a blazing 9600 bps, some router models will allow you to increase the console speed to as high as 115200. Increasing the console speed has its advantages. At face value, it will enhance the response time when typing at the console and will allow console messages to be sent to the console faster. But more importantly, it is useful for those times when you have to upgrade the IOS through the console port.
To change the console speed, you simply use the speed command in line-configuration mode for console 0. The syntax for the speed command is speed . Options may vary on different platforms. Once you change the console speed, you will no longer have console access through your existing terminal setting. You will have to change the console setting on your terminal emulation program to match.
