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The Bryant Advantage Ultimate CCNA Lab Workbook
Chris Bryant, CCIE #12933 - www.thebryantadvantage.com Back To Index
IP Addressing Lab
Youve got to know how to assign IP addresses to pass the CCNA exams,and youre about to get a lot of practice. Were going to configurephysical interfaces, logical interfaces, and loopback interfaces.
You also need to know how to name a router. We do this with thehostname command. Change the names of the routers to whatever youlike, but after practicing this command, change the names back to R1,
R2, R3, SW1, and SW2. Those are the names youll see through the labworkbook.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#hostname Router1Router1(config)#hostname R1
R1(config)#^Z
R1#
The ^Z youll see on the screen is what ctrl-z sends to the console, and
of course, you know from your CCNA reading that ctrl-z brings you backout to the enable prompt.
Notice that the hostname command took effect immediately, as all globalcommands do.
Lets take a look at the networks well be configuring.
Here's a drawing of the network (ignore the OSPF commands -- for
now :) .
Network Type Network / SubnetMask
Ethernet (R2, R3) 172.23.23.0 /27
Serial to Frame Relay Cloud (All) 172.12.123.0 /24
Directly Connected Serial Interfaces(R1, R3)
172.12.13.0 /24
Router 1 Loopback Address 1.1.1.1 / 32
Router 2 Loopback Address 2.2.2.2 /32
Router 3 Loopback Address 3.3.3.3 / 32
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Lets start with R1. DO NOT OPEN THE SERIAL 0 INTERFACE.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface serial0
R1(config-if)#ip address 172.12.123.1 255.255.255.0
R1(config-if)#interface serial1
R1(config-if)#ip address 172.12.13.1 255.255.255.0
R1(config-if)#no shut
00:18:34: %LINK-3-UPDOWN: Interface Serial1, changed state to down
R1(config-if)#interface loopback0
R1(config-if)#ip address 1.1.1.1 255.255.255.255
R1(config-if)#write (OR copy run start)
Building configuration.
Dont worry about the line protocols being down; other labs will take careof that. All were doing right now is setting the IP addresses and openingthe interfaces. Get used to saving your work as often as possible withwr, short for write. Use IOS Help to see the options and the defaults.(Remember, IOS Help is the question mark symbol.) You can also usecopy run start.
Dont forget to open the interfaces! If youre having a connectivity problemand run a command such as show interface ethernet 0, and you see thefollowing, it means the interface is manually closed and needs to be
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opened with the no shutdown command.
R2#show interface ethernet0
Ethernet0 is administratively down, line protocol is down
Now configure R2s interfaces. Do not open interface serial0.
R2(config)#interface serial0
R2(config-if)#encap frame
R2(config-if)#no frame inverse-arp
R2(config-if)#interface serial 0.123 multipoint
R2(config-subif)#ip address 172.12.123.2 255.255.255.0
R2(config-if)#interface ethernet0
R2(config-if)#ip address 172.23.23.2 255.255.255.224
R2(config-if)#no shut
00:28:45: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up
00:28:46: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
changed state to up
R2(config-if)#interface loopback0R2(config-if)#ip address 2.2.2.2 255.255.255.255
R2(config-if)#^Z
R2#
Note that you configured frame relay on R2. That allows us to create themultipoint subinterface. Frame Relay will be covered completely in a laterlab, but you cannot create that multipoint interface until youve enabledframe relay.
Also notice that you dont have to run no shuton a loopback interface.(Its not wrong if you do, but you dont have to.)
Lets configure R3s interfaces. Do not open interface serial0.
R3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#interface serial 0
R3(config-if)#encap frame
R3(config-if)#no frame inverse-arp
R3(config-if)#interface serial0.31 point-to-point
R3(config-subif)#ip address 172.12.123.3 255.255.255.0
R3(config-subif)#interface serial 1
R3(config-if)#ip address 172.12.13.3 255.255.255.0
R3(config-if)#no shut
00:33:32: %LINK-3-UPDOWN: Interface Serial1, changed state to up
00:33:33: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed
state to up
R3(config-if)#interface ethernet0
R3(config-if)#ip address 172.23.23.3 255.255.255.224
R3(config-if)#no shut
00:33:46: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up
00:33:47: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0,
changed sta te to up
R3(config-if)#interface loopback0
00:33:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed
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state to down
R3(config-if)#ip address 3.3.3.3 255.255.255.255
Again, note that you configured frame relay on the serial0 physicalinterface, then created a point-to-point subinterface. The Serial0 physicalinterface then had to be opened.
I urge you to not just walk through these labs, but to use the showanddebugcommands youll read about in this book, in my Ultimate CCNAStudy Guide, and to use IOS Help often to see the other options. Takeadvantage of the fact that youre working with real Cisco routers andswitches, not "router simulators".
You do not need to configure IP addresses on the switches.
Theres another command Id like to introduce you to, since we all mistypefrom time to time. Notice what happens when you mistype a commandon a Cisco router:
R3#hudjgmg
Translating "hudjgmg"...domain server (255.255.255.255)
% Unknown command or computer name, or unable to find computer address
By default, a Cisco router or switch is going to attempt to resolve amistyped command via DNS. Thats what the domain server is that itslooking for, and of course you know that 255.255.255.255 is a layer 3broadcast.
This only takes about 15 seconds to come back with the unknown
command line in a practice lab, but it can take much longer in aproduction network. To disable this default behavior, use the globalcommand no ip domain-lookup on each device in your pod. Notice thatimmediately after using this command, the router tries to resolve thecommand locally but does not send the broadcast out.
R3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#no ip domain-lookup
R3(config)#^Z
R3#jfujjke
Translating "jfujjke"
% Unknown command or computer name, or unable to find computer address
As with all commands you read about and practice with in my books, donot run a command on a production network unless you are sure of theresult. VERY sure. This is particularly true of the debugs youll be using inmy labs.
Congratulations! Youve now configured plenty of IP addresses. If youreconfronted with that task on one of your CCNA exams, youre more thanready. Just dont forget to open the interfaces on exam day!
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