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Nat Sim

June 24th, 2011 in LabSim Go to comments

Question

A network associate is configuring a router for the weaver company to provide internet access. The ISP has provided the company six public IP addresses of 198.18.184.105 198.18.184.110. The company has 14 hosts that need to access the internet simultaneously. The hosts in the company LAN have been assigned private space addresses in the range of 192.168.100.17 – 192.168.100.30.

The following have already been configured on the router:

- The basic router configuration
– The appropriate interfaces have been configured for NAT inside and NAT outside
– The appropriate static routes have also been configured (since the company will be a stub network, no routing protocol will be required.)
– All passwords have been temporarily set to “cisco”

ccna_nat_sim_lab1 ccna_nat_sim_lab2

Solution:

Note: If you are not sure about NAT or Access list, my read my NAT tutorial and Access-list tutorial.

The company has 14 hosts that need to access the internet simultaneously but we just have 6 public IP addresses from 198.18.184.105 to 198.18.184.110/29. Therefore we have to use NAT overload (or PAT) Double click on the Weaver router to open it

Router>enable
Router#
configure terminal

First you should change the router’s name to Weaver

Router(config)#hostname Weaver

Create a NAT pool of global addresses to be allocated with their netmask.

Weaver(config)#ip nat pool mypool 198.18.184.105 198.18.184.110 netmask 255.255.255.248

Create a standard access control list that permits the addresses that are to be translated

Weaver(config)#access-list 1 permit 192.168.100.16 0.0.0.15

Establish dynamic source translation, specifying the access list that was defined in the prior step

Weaver(config)#ip nat inside source list 1 pool mypool overload

This command translates all source addresses that pass access list 1, which means a source address from 192.168.100.17 to 192.168.100.30, into an address from the pool named mypool (the pool contains addresses from 198.18.184.105 to 198.18.184.110).

Overload keyword allows to map multiple IP addresses to a single registered IP address (many-to-one) by using different ports.

The question said that appropriate interfaces have been configured for NAT inside and NAT outside statements. This is how to configure the NAT inside and NAT outside, just for your understanding:

Weaver(config)#interface fa0/0
Weaver(config-if)#
ip nat inside
Weaver(config-if)#
exit
Weaver(config)#
interface s0/0
Weaver(config-if)#
ip nat outside
Weaver(config-if)#end

Finally, we should save all your work with the following command:

Weaver#copy running-config startup-config

Check your configuration by going to “Host for testing” and type:

C:\>ping 192.0.2.114

The ping should work well and you will be replied from 192.0.2.114

You can download this sim and practice with Packet Tracer here: http://www.9tut.com/download/9tut.com_CCNA_NAT_sim_question.zip

(Notice: you can find other NAT Sim Question here)

Other lab-sims in ICND2 Exam:

ICND 2 – OSPF Sim
VTP SIM (on 9tut.com)

EIGRP Lab sim (on 9tut.com)

Other lab-sims might appear in the real ICND 2 exam, read and understand them if you have enough time!

Comments
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  1. Oliver
    January 3rd, 2015

    Well, it will work only if you use the following command, But I am not sure by using this it is going match the access list with our pre-defined pool or not.

    ip nat inside source list 1 interface serial 1/0 overload

  2. João Felipe
    January 22nd, 2015

    I wonder if the command “ip access-group 1 in”, at interface fa 0/0, is necessary too.
    THX

  3. Anonymous
    January 25th, 2015

    question….if you use “wr mem” instead of “copy run start” do you lose credit?

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