Configuring a Router
Router Modes
| Router> | User mode |
| Router# | Privileged mode |
| Router(config)# | Global configuration mode |
| Router(config-if)# | Interface mode |
| Router(config-subif)# | Subinterface mode |
| Router(config-line)# | Line mode |
| Router(config-router)# | Router configuration mode |
Global Configuration Mode
| Router> | Can see config, but not change |
| Router# | Can see config and move to make changes |
| Router#config t | Moves to global config mode |
| Router(config)# | This prompt indicates that you can start making changes |
Configuring a Router Name
| Router(config)#hostname Cisco | Name can be any word you choose |
Configuring Passwords
| Router(config)#enable password cisco | Sets enable password |
| Router(config)#enable secret password class | Sets enable secret password |
| Router(config)#line con 0 Router(config-line)#password console Router(config-line)#login | Enters console-line mode Sets console-line mode password to console |
| Router(config)#line vty 0 4 Router(config-line)#password telnet Router(config-line)#login | Enters vty line mode for all 5 vty lines Sets vty password to telnet Enables password checking at login |
| Router(config)#line aux 0 Router(config-line)#password backdoor Router(config-line)#login | Enters auxiliary line mode Sets auxiliary line mode password to backdoor Enables password checking at login |
Password Encryption
| Router(config)#service password-encryption | Applies a weak encryption to passwords |
Show Commands
| Router#show ? | Lists all show commands available |
| Router#show interfaces | Displays statistics for all interfaces |
| Router#show interfaces serial 0 | Displays statistics for a specific interface, in this case Serial 0 |
| Router#show ip interface brief | Displays a summary of all interfaces, including status and IP address assigned |
| Router#show controllers serial 0 | Displays statistics for interface hardware. Statistics display if the clock rate is set and if the cable is DCE, DTE, or not attached |
| Router#show clock | Displays time set on device |
| Router#show hosts | Displays local host-to-IP address cache. These are the names and addresses of hosts on the network to which you can connect |
| Router#show users | Displays all users connected to device |
| Router#show history | Displays history of commands used |
| Router#show flash | Displays info about Flash memory |
| Router#show version | Displays info about loaded software version |
| Router#show arp | Displays the ARP table |
| Router#show protocols | Displays status of configured Layer 3 protocols |
| Router#show startup-config | Displays configuration saved in NVRAM |
| Router#show running-config | Displays configuration currently running in RAM |
Configuring a Serial Interface
| Router(config)#int s0/0 | Moves to interface Serial 0/0 mode |
| Router(config-if)#description Link to ISP | Optional descriptor of the link is ocally significant |
| Router(config-if)#ip address 192.168.10.1 255.255.255.0 | Assigns address and subnet mask to interface |
| Router(config-if)#clock rate 56000 | Assigns a clock rate for the interface |
| Router(config-if)#no shut | Turns interface on |
TIP: The clock rate command is used only on a serial interface that has a DCE cable plugged into it. There must be a clock rate set on every serial link between routers. It does not matter which router has the DCE cable plugged into it, or which interface the cable is plugged into. Serial 0 on one router can be plugged into Serial 1 on another router.
Configuring an Ethernet/Fast Ethernet Interface
| Router(config)#int fa0/0 | Moves to Fast Ethernet 0/0 interface mode |
| Router(config-if)#description Accounting LAN | Optional descriptor of the link is locally significant |
| Router(config-if)#ip address 192.168.20.1 255.255.255.0 | Assigns address and subnet mask to interface |
| Router(config-if)#no shut | Turns interface on |
Creating a MOTD Banner
| Router(config)#banner motd # This is a secure system. Authorized Personnel Only # | # is known as a delimiting character. The delimiting character must surround the banner message and can be any character so long as it is not a character used within the body of the message |
Assigning a Local Host Name to an IP Address
| Router(config)#ip host london 172.16.1.3 | Assigns a host name to the IP address. After this assignment, you can use the host name instead of an IP address when trying to Telnet or ping to that address |
Setting the Clock Time Zone
| Router(config)#clock timezone EST –5 | Sets the time zone for display purposes. Based on coordinated universal time (Eastern Standard Time is 5 hours behind UTC) |
no ip domain-lookup Command
| Router(config)#no ip domain-lookup | Turns off trying to automatically resolve an unrecognized command to a local host name |
TIP: Ever type in a command incorrectly and left having to wait for a minute or two as the router tries to translate your command to a domain server of 255.255.255.255? The router is set by default to try to resolve any word that is not a command to a DNS server at address 255.255.255.255. If you are not going to set up DNS, turn this feature off to save you time as you type, especially if you are a poor typist.
logging synchronous Command
| Router(config)#line con 0 Router(config-line)#logging synchronous | Turns on synchronous logging. Information items sent to console will not interrupt the command you are typing. The command will be moved to a new line |
exec-timeout Command
| Router(config)#line con 0 Router(config-line)#exec-timeout 0 0 | Sets time limit when console automatically logs off. Set to 0 0 (minutes seconds) means console never logs off |
Saving Configurations
| Router(config)copy run start | Saves the running-config to local NVRAM |
| Router(config)copy run tftp | Saves the running-config remotely to TFTP server |
Erasing Configurations
| Router#erase start | Deletes the startup-config file from NVRAM |
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