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Chapter 4
Introduction to the Cisco IOS
Another way to check an interface's status is via the show running-config
command. All interfaces are shut down by default.
Router#sh int ethernet0
Ethernet0 is administratively down, line protocol is down
[output cut]
Bring up the interface with the no shutdown command.
Router#config t
Enter configuration commands, one per line. End with
CNTL/Z.
Router(config)#int ethernet0
Router(config-if)#no shutdown
Router(config-if)#^Z
00:57:08: %LINK-3-UPDOWN: Interface Ethernet0, changed
state to up
00:57:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Ethernet0, changed state to up
Router#sh int ethernet0
Ethernet0 is up, line protocol is up
[output cut]
Configuring an IP Address on an Interface
Even though you don't have to use IP on your routers, it's most often what
people use. To configure IP addresses on an interface, use the ip address
command from interface configuration mode:
Router(config)#int e0
Router(config-if)#ip address 172.16.10.2 255.255.255.0
Router(config-if)#no shut
Don't forget to turn on an interface with the no shutdown command (no
shut
for short). Remember to look at the command show interface e0, for
example, to see if it's administratively shut down or not. Show running-
config
will also give you this information.
The ip address address mask command starts the IP processing on the
interface.
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