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RENJIN BOSE R.K
In our last article I show you that how can you connect Cisco router. In this article I will show how can you can configure router. For demonstration purpose I used packet tracer software. If you haven’t install packet tracer read our pervious article to download and install packet tracer. Link is given on the top side of left. Create a simple topology by dragging dives on workspace as shown in figure.
Click inside the Router and select CLI and press Enter to get started. Setup mode start automatically if there is no startup configuration present. The answer inside the square brackets [ ], is the default answer. If this is the answer you want, just press enter. Pressing CTRL+C at any time will end the setup process, shut down all interfaces, and take you to user mode (Router>).
You cannot use setup mode to configure an entire router. It does only the basics. For example, you can only turn on either RIPv1 or Interior Gateway Routing Protocol (IGRP), but not Open Shortest Path First Protocol (OSPF) or Enhanced Interior Gateway Routing Protocol (EIGRP). You cannot create access control lists (ACL) here or enable Network Address Translation (NAT). You can assign an IP address to an interface, but not to a subinterface. All in all, setup mode is very limiting.
In Privilege mode(indicated by the '#', you can do anything). To get into privilege mode the keyword is enable.
Next type the command enable to get to the privileged mode prompt.
CAUTION: The enable secret password is encrypted by default. The enable password is not. For this reason, recommended practice is that you never use the enable password command. Use only the enable secret password command in a router or switch configuration.
You cannot set both enable secret password and enable password to the same password. Doing so defeats the use of encryption.
# is known as a delimiting character. The delimiting character must surround the banner and login message and can be any character so long as it is not a character used within the body of the message
Ever type in a command incorrectly and are 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 Domain Name System (DNS) server at address 255.255.255.255. If you are not going to set up DNS, turn off this feature to save you time as you type, especially if you are a poor typist
The command exec-timeout 0 0 is great for a lab environment because the console never logs out. This is considered to be bad security and is dangerous in the real world. The default for the exec-timeout command is 10 minutes and zero (0) seconds (exec-timeout 10 0).
Click inside the Router and select CLI and press Enter to get started.
You cannot use setup mode to configure an entire router. It does only the basics. For example, you can only turn on either RIPv1 or Interior Gateway Routing Protocol (IGRP), but not Open Shortest Path First Protocol (OSPF) or Enhanced Interior Gateway Routing Protocol (EIGRP). You cannot create access control lists (ACL) here or enable Network Address Translation (NAT). You can assign an IP address to an interface, but not to a subinterface. All in all, setup mode is very limiting.
--- System Configuration Dialog ---
Continue with configuration dialog? [yes/no]:
Write no and press enter. To get router prompt You are now connected to Router and are in user mode prompt. The prompt is broken down into two parts, the hostname and the mode. “Router” is the Router0's hostname and “>” means you are in user mode.Press RETURN to get started Router>User mode is indicated with the '>' next to the router name. in this mode you can look at settings but can not make changes.
In Privilege mode(indicated by the '#', you can do anything). To get into privilege mode the keyword is enable.
Next type the command enable to get to the privileged mode prompt.
Router > enable Router#To get back to the user mode, simply type disable. From the user mode type logout or exit to leave the router.
Router#disable Router> Router>exit Router con0 is now available Press RETURN to get startedpress enter to get back router prompt
Router>You are now in User mode. Type ?to view all the available commands at this prompt.
Router>?From privilege mode you can enter in configuration mode by typing configure terminal you can exit configuration mode type exit or <CTL>+z
Router>enable Router#config terminal Router(config)#exit Router#
To read more about Cisco mode read our previous article
To view all commands available from this mode type ? and press enter This will give you the list of all available commands for the router in your current mode. You can also use the question mark after you have started typing a command. For example if you want to use a show command but you do not remember which one it uses 'show ?' will output all commands that you can use with the show command.Router#show ? access-expression List access expression access-lists List access lists backup Backup status cdp CDP information clock Display the system clock cls DLC user information compress Show compression statistics configuration Contents of Non-Volatile memory --More--
Basic Global Configurations mode Commands
Configuring a Router Name
This command works on both routers and switchesRouter(config)#hostname Lucknow
Lucknow(config)#
You could choose any descriptive name for your cisco devices Configuring Passwords
This command works on both routers and switches| Router(config)#enable password test | Sets enable password to test |
| Router(config)#enable secret vinita | Sets enable secret password to vinita |
| Router(config)#line console 0 | Enters console line mode |
| Router(config-line)#password console | Sets console line mode password to console |
| Router(config-line)#login | Enables password checking at login |
| Router(config)#line vty 0 4 | Enters vty line mode for all five vty lines |
| Router(config-line)#password telnet | Sets vty password to telnet |
| Router(config-line)#login | Enables password checking at login |
| Router(config)#line aux 0 | Enters auxiliary line mode |
| Router(config-line)#password aux | Sets auxiliary line mode password to aux |
| Router(config-line)#login | Enables password checking at login |
You cannot set both enable secret password and enable password to the same password. Doing so defeats the use of encryption.
Configuring a Fast Ethernet Interface
| Router(config)#interface fastethernet 0/0 | Moves to Fast Ethernet 0/0 interface configuration mode |
| Router(config-if)#description Student Lab 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 shutdown | Turns interface on |
Creating a Message of the Day Banner
Router(config)#banner motd # Next Schedule metting with manager is Postponed # Router(config)#The MOTD banner is displayed on all terminals and is useful for sending messages that affect all users. Use the no banner motd command to disable the MOTD banner. The MOTD banner displays before the login prompt and the login banner, if one has been created.
Creating a Login Banner
Router(config)#banner login # Unauthorized access is prohibited ! Please enter your username and password. # Router(config)#The login banner displays before the username and password login prompts. Use the no banner login command to disable the login banner. The MOTD banner displays before the login banner.
# is known as a delimiting character. The delimiting character must surround the banner and login 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 Lucknow 172.16.1.1Assigns a host name to the IP address. After this assignment, you can use the host name rather than an IP address when trying to Telnet or ping to that address
The no ip domain-lookup Command
Router(config)#no ip domain-lookup Router(config)#Turns off trying to automatically resolve an unrecognized command to a local host name
Ever type in a command incorrectly and are 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 Domain Name System (DNS) server at address 255.255.255.255. If you are not going to set up DNS, turn off this feature to save you time as you type, especially if you are a poor typist
The logging synchronous Command
Router(config)#line console 0 Router(config-line)#exec-timeout 0 0 Router(config-line)#Sets the time limit when the console automatically logs off. Set to 0 0 (minutes seconds) means the console never logs off.
The command exec-timeout 0 0 is great for a lab environment because the console never logs out. This is considered to be bad security and is dangerous in the real world. The default for the exec-timeout command is 10 minutes and zero (0) seconds (exec-timeout 10 0).
Saving and erasing configurations
| Router(config)#exit | Bring you back in Privilege exec mode |
| Router#copy running-config startup-config | Saves the running configuration to local NVRAM |
| Router#copy running-config tftp | Saves the running configuration remotely to a TFTP server |
| Router#erase startup-config | Deletes the startup configuration file from NVRAM |
Configuration Example: Basic Router Configuration
For example purpose we will use the topology created in start of this article. Create a simple topology by dragging dives on workspace as shown in figure.--- System Configuration Dialog --- Continue with configuration dialog? [yes/no]: no Press RETURN to get started! Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#hostname R1 R1(config)#interface fastethernet 0/0 R1(config-if)#description Student Lab LAN R1(config-if)#ip address 192.168.20.1 255.255.255.0 R1(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up R1(config-if)#exit R1(config)#banner motd # Next Schedule metting with is postponed # R1(config)#banner login # Unauthorized access is prohibited ! Enter you user name and password # R1(config)#ip host Lucknow 172.16.1.1 R1(config)#no ip domain-lookup R1(config)#line console 0 R1(config-line)#exec-timeout 0 0 R1(config-line)#logging synchronous R1(config-line)#password consloe R1(config-line)#login R1(config-line)#exit R1(config)#line vty 0 4 R1(config-line)#password telnet R1(config-line)#login R1(config-line)#exit % Unrecognized command R1(config)#enable password test R1(config)#enable secret vinita R1(config)#exit %SYS-5-CONFIG_I: Configured from console by console R1#copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] R1#
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