Configuring a Router
Module 3
Semester 2
Router Configuration Tasks
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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
Router Modes
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All configuration changes are made from Global Config mode
Ctrl-Z or end
– returns to Privileged EXEC mode
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exit
– Go back one step
Configure Hostname
• Required if name resolution is to be used
• Not essential for the functioning of our routers but is important
Configuring passwords
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An important feature
– security
– telnet (vty) will not work without a
password set
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Line console 0
– sets login password for User
EXEC mode
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Enable password xxx
– sets login password for Privileged
EXEC mode
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Enable secret
– sets encrypted password for
Privileged EXEC mode
– (strong encryption)
Show Commands
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show interfaces – Displays statistics
for all interfaces on a router.
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Router#show interfaces serial 0/1
show controllers serial - Displays
information that is specific to the
interface hardware. This command
must also include the port or slot/port
number of the serial interface.
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show history - Displays a history of
commands that have been entered
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show flash - Displays information
about flash memory and what IOS files
are stored there
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show version - Displays information
about the currently loaded software
version along with hardware and
device information
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show arp - Displays the ARP table of
the router
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show protocols - Displays the global
and interface-specific status of any
configured Layer 3 protocols
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show startup-config - Displays the
saved configuration located in NVRAM
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show running-config
Router#show controllers serial 0/1
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show clock - Shows the time set in
the router
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show hosts - Displays a cached list of
host names and addresses
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show users - Displays all users who
are connected to the router
Configuring an interface
Configuring an Ethernet Interface
Configuring a Serial Interface
Fast Ethernet Interface
Router(config)# interface fastethernet 0/0
Router(config-if)# ip address 190.100.11.1 255.255.255.0
Router(config-if)# no shutdown
Serial Interface (DCE)
(no clock for DTE)
Router(config)# interface serial 0/0
Router(config-if)# ip address 190.100.10.2 255.255.255.0
Router(config-if)# clock rate 56000
Router(config-if)# no shutdown
Configuring Interface Descriptions
An interface description should identify important
information such as a router, a circuit number, or a
specific network segment.
The Login Banner
• The Banner is seen when someone attempts to login
• Important to let user know it is a private system
Login Banner MOTD
• Configured from Global Config mode
• Use the Banner MOTD command
• Use delimiters (#) to indicate start and end of message
Host Name Resolution
• Two Choices
– DNS
• Dynamic
• (not available in our lab)
– Hosts Table
• Static entries
• Used in our lab situation
Configuring Hosts Tables
• The Host table contains:
– Name
– IP address of each router in the network
• The host name in a command will be resolved to an IP
address if the name is found in the table
– i.e. ping Auckland
– is translated to ping 172.16.32.1 (if the hosts below entered)
• Host tables only apply to the the local router
The copy running-config tftp Command
Backing up Configuration Files
The copy tftp running-config Command
Restoring Configuration Files from a TFTP Server
Changing Router Configuration
Configuration Standards
• Configuration Standards may specify:
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How the files are stored
Where the files are stored
Naming conventions
Who has access
Coding standards – e.g. comments, sections, etc
Interface descriptions
TUGAS-sImple Example
Subnets
10.0.0.0/16
10.1.0.0/16
10.2.0.0/16
10.2.0.0/24
10.2.1.0/24
10.2.2.0/24
Etc.
10.2.255.0/24
10.3.0.0/16
Etc.
10.255.0.0/16
An example of VLSM, NOT of good network design.
10.1.0.0/16
10.2.0.0/24
10.2.1.0/24
10.7.0.0/16
10.3.0.0/16
10.2.6.0/24
10.4.0.0/16
10.2.3.0/24
10.2.8.0/24
10.5.0.0/16 10.8.0.0/16
10.2.5.0/24
10.6.0.0/16
10.2.4.0/24
• Your network can now have 255 /16 subnets with 65,534 hosts each
AND 256 /24 subnets with 254 hosts each.
• All you need to make it work is a classless routing protocol that passes
the subnet mask with the network address in the routing updates.
• Classless routing protocols: RIPv2, EIGRP, OSPF, IS-IS, BGP