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Helpful Cisco Commands

Stop the annoying debug console messages on the telnet prompt

  • Router#Terminal no monitor

Encrypting All Passwords on the Router.

  • Router(config)#service password-encryption
  • By default the only password that is encrypted in an IOS router is the enable password.  It should be noted that the ‘service password-encryption’ command uses a proprietary Vigenere cipher to encrypt all passwords on the router except for the enable password.  The enable password uses MD5.  The Vigenere cipher is easy to decrypt using readily available tools like GETPASS.  Below, the bold ‘7’ indicates the password has been encrypted using the Vigenere cipher.  Usernames can be encrypted using stronger encryption algorithms and aren’t as easily cracked.
  • line con 0
    password 7 110A1016141D
    logging synchronous
    login
    transport input none

DNS Lookup

  • Recognize this when you make a typo?
    Router#line 1
    Translating "line"...domain server (8.8.8.8)
    
    Translating "line"...domain server (8.8.8.8)
    
    Translating "line"...domain server (8.8.8.8)
    
    % Bad IP address or host name
    % Unknown command or computer name, or unable to find computer address

    Stop it from happening with the following command:

  • Router(config)#no ip domain-lookupTurn it back on with the following code:
  • Router(config)#ip domain-lookup
  • You will not be able to ping host names while domain lookup is turned off. You can still ping IP addresses.