Router Configuration PJC CCNA Semester 2 Ver. 3.0 by William Kelly

Command Modes The router has two main modes: user exec mode for monitoring and user privileged exec mode for monitoring and changing the configuration Enter the privileged mode with the enable command Enter the global configuration mode with the configure command To configure from the terminal use terminal Enter the specific mode Typing exit leaves a specific config mode and the Ctl- Z key combination leaves the global config mode entirely and returns to the privileged mode prompt Note: Understand how the prompts change at each level

Router Startup Modes ROM Monitor Mode – used for password recovery or system failure recovery Setup – used for initial setup RXBoot – limited set of commands to enable a new IOS to be loaded from a tftp server

Router Configuration Commands configure terminal configure memory copy tftp running-config show running-config copy running-config startup-config copy running-config tftp show startup-config erase startup-config

Configuring the Router Name Router(config)# hostname moscow moscow(config)#

Protecting Router Passwords The enable secret uses md5 one way strong encryption (This method cant currently be unencrypted) Weak encryption can be used with the following command: Router(config)# service password encryption

Information from show Commands Be aware of the information each show command gives you if you needed to choose the correct output from a list

Configuring Serial and Ethernet Interfaces Serial Interface Router(config)# interface serial 1/0 Router(config-if)# Router(config-if)# clockrate Router(config-if)# no shutdown Ethernet Interface Router(config)# interface ethernet 1/0 Router(config-if)# Router(config-if)# no shutdown

Executing Router Changes Interfaces are powered on by the no shutdown command A no in front of a command usually reverses the command Contents of NVRAM are managed by the erase start, copy run start, and show start commands

Configuration Standards, Backup, and Documentation Organization wide standards aids in maintaining configurations Standards help reduce complexity, downtime, and exposure to unusual events that impact the network Router configurations should be backed up to disk or remote servers (tftp servers)

Interface Descriptions Setting an Interface Description Router(config)# interface ethernet 0 Router(config-if)# description crystal peak secure LAN Router(config-if)# exit

Login Banners Login banners display messages at login Anyone can see a login banner so unwanted visitors should be warned that it is illegal to attempt to access the system Router(config)# banner login # You are attempting to access SKYNET. This connection is being traced and attempts at unauthorized entry will be referred to our HK Investigation Division!#

Message of the Day (MOTD) MOTD can only been seen by users who have successfully logged in Router(config)# banner motd # You are logged into SKYNET. Have a nice day!#

Host Name Resolution A host table allows names to be translated to ip addresses Host names are only meaningful on the router on which they are configured (they are not the same as DNS) Router(config)# ip host moscow Router(config)# ip host perm

Password Recovery The technique varies from router to router but the general points are as follows: The config-register is recorded is possible from the show version command The normal boot prompt is interrupted (Ctrl-break) The configuration register is changed perhaps from 0x2102 to 0x42 using o/r 0x42 after interrupted the boot The router is rebooted using i The password is bypassed A new password is entered The config register is reset with config-register 0x2102 at global config The router is rebooted to test the password change