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Ch.3 – Configuring a Router
CCNA 1 version 3.0
Overview
Students completing this module should be able to: • Name a router • Set passwords • Examine show commands • Configure a serial interface • Configure an Ethernet interface • Execute changes to a router • Save changes to a router • Configure an interface description • Configure a message-of-the-day banner • Configure host tables • Understand the importance of backups and documentation
CLI command modes
Router#configure terminalRouter(config)#
exit
end
Using exit, end and Control-Z
Router>enaRouter#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)#?Configure commands: aaa Authentication, Authorization and Acc.. access-list Add an access list entry alias Create command alias appletalk Appletalk global configuration commands arap Appletalk Remote Access Protocol arp Set a static ARP entry<text omitted> Router(config)#exit00:03:20: %SYS-5-CONFIG_I: Configured from console by conRouter#
Router(config)#interface interfaceRouter(config-if)#exitRouter(config)#router routing-protocolRouter(config-router)#exitRouter(config)#exitRouter#
Message each time you exit “global configuration mode”
Must be in privileged mode
Using exit, end and Control-Z
Router# conf t (abbreviated)
Router(config)# router protocolRouter(config-router)# (commands)Router(config-router)# exitRouter(config)# exitRouter#
Router(config)# interface type portRouter(config-if)# (commands)Router(config-if)# end (or Control-Z)Router#
Using exit, end and Control-Z
Configuring a router name
Router#config t
Router(config)#hostname Tokyo
Tokyo(config)#
Lab 12-1: Command Mode and Router Identification: Page 244
Configuring router passwords
Not recommended, clear text
Router(config)#enable secret <password>Use this command instead, password is encryped
Encrypts the passwords above, but…
WARNING
• service password-encryption uses a Cisco Level 7 encryption which is very easy to decrypt.
• For the GetPass! software www.boson.com
• However, the enable secret <password> uses a stronger encryption method and cannot be easily hacked.
service password-encryption command
Doesn’t work for enable secret!
• More later!
enable secret <password> command
Lab 12-2: Configuring Router Passwords. Page 247
Router Passwords Used in the Cisco Lab
Privilege Password cisco
Console password conpass
VTY 0 4 password vtypass
Auxiliary auxpass
Examining the show commands
• show interfaces – Displays all the statistics for all the interfaces on the router. To view the statistics for a specific interface, enter the show interfaces command followed by the specific interface and port number.
• show controllers serial – Displays information-specific to the interface hardware
• show clock – Shows the time set in the router • show hosts – Displays a cached list of host names and addresses • show users – Displays all users who are connected to the router • show history – Displays a history of commands that have been entered • show flash – Displays information about flash memory and what IOS files are
stored there • show version – Displays information about the router and the IOS that is
running in RAM • show ARP – Displays the ARP table of the router • show protocol – Displays the global and interface specific status of any
configured Layer 3 protocols • show startup-configuration – Displays the saved configuration located in
NVRAM
• show running-configuration – Displays the configuration currently running in RAM
Router>show interface ethernet 0Ethernet0 is administratively down, line protocol is down , using hub 0 Hardware is Lance, address is 0010.7b3a.cf84 (bia 0010.7b3a.cf84) MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00 Last input never, output 01:05:35, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 input packets with dribble condition detected 63 packets output, 11676 bytes, 0 underruns 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped outRouter>
Status MAC Address
Routing metric information (later)
Data link encapsulation
(Ethernet-II)
ARP cache entries timer
show interfaces <interface> command
Examining the show commands
• We will log into a router and examine some of the show commands.
Lab 12-3: Using Router Show Commands, Page 251
Configuring a serial interface
Router(config)#interface serial 0/0
Router(config-if)#ip address <ip address> <netmask>
Configuring an IP Address on an interface…
show ip interface command
• A serial interface will not show “up” and “up” unless both ends are properly configured (mostly) and the no shutdown command is used.
• If one router’s configuration looks okay, check the other router’s configuration.
Router# show ip interface brief
Interface IP-Address OK? Method Status Protocol
Ethernet0 131.108.1.11 YES manual up up
Serial0 198.135.2.49 YES manual administratively down down
What is wrong here? The administrator has either done a “shutdown” on the interface or has forgotten to do a “no shutdown”.
Lab
Real world
• On serial links that are directly interconnected, as in a lab environment, one side must be considered a DCE and provide a clocking signal.
• The clock is enabled and speed is specified with the clock rate command.
Router(config)#interface serial 0/0
Router(config-if)#clock rate 56000
Router(config-if)#no shutdown
Configuring a serial interface
RouterB(config)#inter serial 1RouterB(config-if)#clock rate ? Speed (bits per second) 1200 2400 4800 9600 19200 38400 56000 64000 <text omitted> 2000000 4000000
<300-4000000> Choose clockrate from list above
RouterB(config-if)#clock rate 64000RouterB(config-if)#
RouterB DCE cable
RouterA DTE cable
Configuring a serial interface
How can you tell which end is the DTE and which end is the DCE? Look at the label on the cable. Look at the connecter between the two cables - The DTE cable will
always be male and the DCE cable will always be female.
DTE Cable DCE Cable
Configuring a serial interface
RouterA#show controllers serial 0HD unit 0, idb = 0xECA4C, driver structure at 0xF1EC8buffer size 1524 HD unit 0, V.35 DTE cablecpb = 0x62, eda = 0x403C, cda = 0x4050RX ring with 16 entries at 0x62400000 bd_ptr=0x4000 pak=0x0F5704 ds=0x62FFB8 status=80 pak_size=22
RouterB#show controllers serial 0buffer size 1524 HD unit 0, V.35 DCE cable, clockrate 64000cpb = 0x62, eda = 0x408C, cda = 0x40A0RX ring with 16 entries at 0x62400000 bd_ptr=0x4000 pak=0x0F2F04 ds=0x627908 status=80 pak_size=22
RouterB DCE cable
RouterA DTE cable
How can you tell which end is the DTE and which end is the DCE? Use the show controllers command! It will also tell you the type of cable, in our labs we will be using a V.35
cable.
This is one of few commands where there must be a space between the interface type and the port.
Configuring a serial interface
• Please be very careful when connecting the male and female V.35 cables together AND when connecting the serial cable to the router!
• They only connect ONE WAY!
• Be sure the two ends match!
• Don’t force it!
This end up!
(The wider end is up.)
Configuring a serial interface
Lab 12-4: Configuring a Serial Interface, Page 256
Configuring an Ethernet Interface
Interface descriptions
RouterB#show inter e 0Serial0 is up, line protocol is up Hardware is HD64570 Description: Engineering LAN, Bldg. 18 Internet address is 10.1.1.1/24
Gateway(config)#inter e 0Gateway(config-if)#description LAN interface for MarketingGateway(config-if)#endGateway#Gateway#show runBuilding configuration...<text omitted>!interface Ethernet0 description LAN interface for Marketing no ip address no ip directed-broadcast shutdown<text omitted>
Gateway#show interface ethernet 0Ethernet0 is administratively down, line protocol is down Hardware is Lance, address is 0000.0c34.9ebb (bia 0000.0c34.9ebb) Description: LAN interface for Marketing MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 252/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00<text omitted>Gateway#copy run startDestination filename [startup-config]?Building configuration...Gateway#
Don’t forget this or next time router reboots these changes will be lost!
Interface descriptions
Configuring interface description
Lab 12-5: Configuring an Ethernet Interface, Page 260
Importance of configuration standards
• In order to manage a network, there must be a centralized support standard.
• Configuration, security, performance, and other issues must be adequately addressed for the network to function smoothly.
• Creating standards for network consistency helps reduce network complexity, the amount of unplanned downtime, and exposure to events that may have an impact on network performance.
running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
Executing adds, moves, and changes
Router#show startup-config%% Non-volatile configuration memory is not present
Router#show running-configBuilding configuration...
Current configuration:!version 12.0service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname Router!ip subnet-zero!!interface Ethernet0 no ip address no ip directed-broadcast shutdown!interface Serial0 no ip address no ip directed-broadcast shutdown
No startup-config file in NVRAM
Default running-config file, created in RAM
Executing adds, moves, and changes
The running-config
• The configuration file contains global, process, and interface information that directly affects the operation of the router and its interface ports.
• All changes to the router are made to the running-config file and take affect immediately on the router (with just a couple of exceptions).
– IP address– Routing Protocols– Router’s Name– etc.
Router#show running-configBuilding configuration...Current configuration:!version 12.0service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname Router!ip subnet-zero!interface Ethernet0 no ip address no ip directed-broadcast shutdown
Executing adds, moves, and changes
startup-config
RAMrunning-config
During bootup
• Changes to the router are automatically put in the running-config file.• If the router loses power or reboots, everything in RAM is lost including the running-
config file.• To make sure the changes to the router’s configuration remain saved, you must copy
the running-config from RAM into the startup-config into NVRAM:
Router# copy running-config startup-config
Router# copy running-config startup-config
copy running-config startup-config
Router#copy running-config startup-configDestination filename [startup-config]?Building configuration...
Router#show startup-config!version 12.0service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname Router!!ip subnet-zero!interface Ethernet0 no ip address no ip directed-broadcast shutdown!
The startup-config file now identical to running-config and the router will also have these changes if the router reboots.
copy running-config startup-config
Router# copy running-config startup-config OrRouter# copy running startup ORRouter# copy run start ORAny usage of the command or parameters, so that they are still uniquely recognizable .
WARNING• Using an incorrect configuration file name could overwrite the router’s IOS in flash, as the router believes
you are trying to copy a blank file into flash.
Router#copy running-config start-up **** NOTICE ****Flash load helper v1.0This process will accept the copy options and then terminatethe current system image to use the ROM based image for the copy.Routing functionality will not be available during that time.If you are logged in via telnet, this connection will terminate.Users with console access can see the results of the copy operation. ---- ******** ----Proceed? [confirm]^C%Copy cancelled by user request.Router#
Incorrect file name!
Press <control> C
copy running-config startup-config
Router# copy running-config startup-config
Or
Router# copy running startup
OR
Router# copy run start
OR
Any usage of the command or parameters, so that they are still uniquely recognizable.
WARNING
• This is also incorrect, and will overwrite the startup-config with a blank file.
Router#copy runningconfig startup-config
Destination filename [startup-config]?
?Bad filename
Router#
Incorrect file name!Press <control> C
copy running-config startup-config
show startup-config
show running-config
These commands can only be done in privilege mode because they display password information.
1
Displaying the config files
Executing adds, moves, and changes
Mistake: Should be: copy start run
Reinforcing What We Learned
• Lab 12-6: Making configuration Changes, Page 262
• Lab 12-7: Configuring Interface Descriptions, Page 266
Login banners and Configuring message-of-the-day (MOTD)
Wording is not the same, but you get the idea.
Router(config)#hostname GatewayGateway(config)#Gateway(config)#banner motd #Enter TEXT message. End with the character '#'.Warning!Stay away! #Gateway(config)#endGateway#exitPress RETURN to get started.
Warning!Stay away!
User Access Verification
Password:Gateway#show runBuilding configuration...<text omitted>!hostname Gateway!<text omitted>!banner motd ^CWarning!Stay away! ^C
Delimiter always shows as “^C”
MOTD (Message Of The Day)
Prompt changes
Login banners and Configuring message-of-the-day (MOTD)Lab 12-8: Configuring Message of the Day, Page 269
Host name resolution
Router# ping 172.16.32.1Router# ping Auckland
Router# telnet 192.168.53.1Router# telnet Beirut
Router# traceroute 192.168.89.1Router# traceroute Capetown
• The Cisco IOS software maintains a cache of host name-to-address mappings for use by EXEC commands.
• This cache speeds up the process of converting names to addresses.
• Host names, unlike DNS names, are significant only on the router on which they are configured. (DNS is also an option – later)
Host name resolution
• This does not make the router a DNS (Domain Name Server).
• This command does not turn your router into a DNS server.
• This command does not effect packets entering your router to be routed.
• This only affects the IOS commands entered at the router prompt.
• Multiple ip addresses can be entered in case one interface is down.
• It is usually a good idea to use the same list of names on all your router configs.
Router(config)# ip host SantaCruz 172.16.32.1 192.168.53.1
Configuring Multiple IP Addresses
Configuring host tables
• If you are not using the services of a DNS server, it is best to disable this process.• DNS (Domain Name Service) is enabled by default with a server address of
255.255.255.255, which is a local broadcast. • If enabled, with no DNS server on the network, may cause a slight, but irritable
delay when making typing mistakes.Lab 12-9: Configuring Host Tables, Page 271
Router(config)# ip domain-lookupRouter#wrehTranslating "wreh"...domain server (255.255.255.255) (Takes a few seconds) Translating "wreh"...domain server (255.255.255.255) (Takes a few seconds)
Router(config)# no ip domain-lookupRouter#wreh Translating "wreh"% Unknown command or computer name, or unable to find computer address
Configuration backup and documentation
• Configuration files should be stored as backup files in the event of a problem.
• Configuration files can be stored on a network server, on a TFTP server, or on a disk stored in a safe place.
Copying, editing, and pasting configurations
• A TFTP server will allow image and configuration uploads and downloads over the network.
• The TFTP server can be another router, or it can be a host system.
• The TFTP host can be any system that has TFTP software loaded and operating and able to receive files from the TCP/IP network.
Copying, editing, and pasting configurations
RAMIOS (running)running-config startup-config IOS
copy startup-config tftp
copy tftp startup-config
copy running-config tftp
copy tftp running-config
copy flash tftp
copy tftp flash
Copying, editing, and pasting configurations
Copying, editing, and pasting configurations
• Troubleshooting: Be sure you can ping the TFTP server.
• When using Windows, the TFTP server software must be running.
• The copy can be performed from the console port or from a telnet session.
• The telnet session can be performed on the same computer where the TFTP server is running (or to a different computer).
Router# copy flash tftp
TFTP Software and Servers
• TFTP software either comes free with the OS (Linux/Unix) or can be downloaded for free.
TFTP Software and Servers
• Just double click on the shortcut…• Remember, TFTP is “Trivial” FTP:
– No authentication– No login– No choice for directory– Uses UDP and verified via a TFTP checksum (not TCP ACKs)
Managing Configuration Files with TFTP, Page 323
Cisco TFTP Server.lnk
TFTP Software and Servers
Summary (1/2)
The router has several modes:
• User EXEC mode
• Privileged EXEC mode
• Global configuration mode
• Other configuration modes
The command-line interface may be used to make changes to the configuration:
• Setting the hostname
• Setting passwords
• Configuring interfaces
• Modifying configurations
• Showing configurations
Summary (2/2)
An understanding of the following key points should have been achieved:
• Configuration standards are key elements in the success of any organization maintaining an efficient network.
• Interface descriptions can include important information to help network administrators understand and troubleshoot their networks.
• Login banners and messages-of-the-day provide users with information upon login to the router.
• Host name resolutions translate names to IP addresses to allow the router to quickly convert names to addresses.
• Configuration backup and documentation is extremely important to keep a network operating smoothly.
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