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CCNA NAT SIM Question 2

February 5th, 2014 Go to comments

Question

ccna_nat_sim_lab_3

You work as a network technician at 9tut.com. Study the exhibit carefully. You are required to perform configurations to enable Internet access. The Router ISP has given you six public IP addresses in the 198.18.32.65 198.18.32.70/29 range.
9tut.com has 62 clients that needs to have simultaneous internet access. These local hosts use private IP addresses in the 192.168.6.65 – 192.168.6.126/26 range.
You need to configure Router1 using the PC1 console.
You have already made basic router configuration. You have also configured the appropriate NAT interfaces; NAT inside and NAT outside respectively.
Now you are required to finish the configuration of Router1.

Solution

Note: If you are not sure how NAT & PAT work, please read my Network Address Translation NAT Tutorial. You can download a similar sim to practice here: http://www.9tut.com/download/9tut.com_CCNA_NAT_sim_question.zip

The company has 62 hosts that need to access the internet simultaneously but we just have 6 public IP addresses from 198.18.32.65 to 198.18.32.70/29 => we have to use NAT overload (or PAT)

Double click on PC1 to access Router1′s command line interface

Router1>enable
Router1#configure terminal

Create a NAT pool of global addresses to be allocated with their netmask (notice that /29 = 248)

Router1(config)#ip nat pool mypool 198.18.32.65 198.18.32.70 netmask 255.255.255.248

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

Router1(config)#access-list 1 permit 192.168.6.64 0.0.0.63

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

Router1(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 192.168.6.65 to 192.168.6.126, into an address from the pool named mypool (the pool contains addresses from 198.18.32.65 to 198.18.32.70)

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:

Router1(config)#interface fa0/0
Router1(config-if)#ip nat inside

Router1(config-if)#exit

Router1(config)#interface s0/0
Router1(config-if)#ip nat outside

Before leaving Router1, you should save the configuration:

Router1(config)#end (or Router1(config-if)#end)
Router1#copy running-config startup-config

Check your configuration by going to PC2 and type:

C:\>ping 192.0.2.114

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

Other lab-sims on this site:

CCNA Access List Sim

CCNA NAT SIM Question 1

CCNA Frame Relay Sim

CCNA Configuration SIM Question (RIPv2 SIM)

CCNA VTP SIM

CCNA EIGRP LAB

CCNA Drag and Drop SIM

CCNA Implementation SIM

 

Comments
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  1. richhello
    July 21st, 2011

    Does cisco give partial credit for incomplete answers on simulation questions. Thanks in advance for your help.

  2. MAS
    July 27th, 2011

    for the ISP router,sombody suggested u hav to configure a default route on it before u can ping the isp router but i cant even log on into the router,its not accepting the “cisco” password.
    somone who has succedded in this should pls help.thanks

  3. alex
    July 27th, 2011

    i got same problem as mike………””Hi. I dont understand the NAT pool configuration. From my studies, I learned when you use PAT you apply it to the interface or one IP address. The IP NAT pool starts with the address 198.18.32.65 – 70 but the serial interface is IP address 192.0.2.113. How can the pool “mypool” be natted to a different IP address (192.0.2.113)? why wouldnt you just use the command “ip nat inside source list 1 s0/0 overload” instead? How does the router know how to match the 198.18.32.65- 70 network to the s0/0 192.0.2.113 address? Thanks for any information.””’ plz answer

  4. chand
    August 1st, 2011

    kindly let me know , how we can open the .Pkt extension file.

  5. asimo
    August 2nd, 2011

    i also don’t understand about ip addresss range in “ip nat pool…” command, plz help me !

  6. King’Leo
    August 5th, 2011

    The public interface on the router doesn’t need to be configured with the public addresses provided by the ISP, hence when trafic leaves the interface in question, the ISP already knows from whence it came and also knows how to direct returning packets to the same interface to reach the private LAN. Your responsibility however is simply to configure NAT correctly with the provided addresses and also the inside and outside interfaces. The ISP does the rest.

  7. 9tut
    August 7th, 2011

    @Mike: Mike post about configuring 0.0.0.0 has been removed as he required. In the exam you don’t need to configure a default route on Router1.

  8. Mike
    August 7th, 2011

    @9tut
    Thanks! can you just go ahead and remove all my post? thanks allot !

  9. Ahmad
    August 22nd, 2011

    hello To all there,

    i have configured the same commend but i am not able to ping sueccesfully, i dont know why, is there any one to guide me about it,
    AbdulAhmad.barakzi@yahoo.com

  10. Alvin
    August 23rd, 2011

    Hi there,
    Some other solutions state that
    access-list 1 permit 192.168.6.64 0.0.0.63
    access-list 1 deny any

    Is it necessary for a “deny any” in the real exam?

  11. david
    August 25th, 2011

    i have configured it too but is not pinging…can somebody please help with this or do we need to configure a routing protocol on the routers…

  12. Claudio from Chile
    August 27th, 2011

    Some other testkings say:
    access-list 1 permit 192.168.6.65 0.0.0.62, what is it correct?

    Is necesary writte access-list 1 deny any at final?

  13. xallax
    August 27th, 2011

    @claudio from chile
    when you use wildcard masks it’s like writing down a subnet.

    our subnet is
    192.168.6.64 /26
    192.168.6.64 255.255.255.192

    the wildcard that would represent this entire subnetwork is… 255-192 = 63.
    192.168.6.64 0.0.0.63

  14. Mark
    August 28th, 2011

    I recreated this network in Packet Tracer and it did not work. I had to add a default route to Router1 (config)#ip route 0.0.0.0 0.0.0.0 192.0.2.114 and a static route on the ISP router to the ouside global address the network was using
    (config)#ip route 198.18.32.64 255.255.255.248 192.0.2.113
    After entering these, then the pings would work. Then I could use the show ip nat translations and show ip nat statistics commands. Part of the problem may be that the default routes are preconfigured in the exam so we do not see them and can’t copy them.

  15. Mark
    August 31st, 2011

    Taking the exam in a few hours. Nervous as hell.

  16. meethilesh
    September 1st, 2011

    taking exams in 2 weeks time plz help with new n dumps…exam on 16 sept

  17. laonglaan
    September 6th, 2011

    wondering why answer didn’t include statement (ip access-group 1 out) on the s0/0 interface. Any comments/explanation to this, ta.

  18. Anonymous
    September 6th, 2011

    pls help with latest dumps, didnt finish on first try….osa_ed@hotmail.com

  19. Malav
    September 8th, 2011

    Wondering Isn’t suppose to use ip nat inside source list 1 interface s0/0 overload instead bcoz
    question is asking 62 host to simultaneous access to internet .

  20. ninosh
    September 18th, 2011

    @laonglan no need that statement because we apply this list on ip nat inside source list 1 pool mypool overload. list 1 indicates access list 1

  21. Sajid
    September 21st, 2011

    Any one can tell me..on what basis we give the subnet mark for our Dynamic Pool..?? and PAT pool?

  22. Declan
    September 25th, 2011

    Taking my exams tomorrow, excited hope i could pass it.

  23. Declan Cudowsky
    September 26th, 2011

    Cleared CCNA today, so funny 1000/1000 is my score, ACL, EIGRP, VTP (all here in 9tut), 53 questions, about 3 to 5 question not in collisio/acme but manageable anyway. Thanks 9TUT CCIP here i come.

  24. deep
    September 29th, 2011

    guys wrong packet tracer was posted here this is the same one from the other NAT SIM

  25. Mohd Ishaq
    October 2nd, 2011

    congratulation to my friend M.Ishaq he passed tha exam of ccna with 841.cong…. to you my loving friend…………………….

  26. Bruno
    October 5th, 2011

    @Sajid
    You get that pool and all that address information from your the ISP. And we put that in our configuration. The ISP handles that some how. So it is just to accept that address space and put it in the configuration. I hope that was a little help.

  27. tornado
    October 6th, 2011

    Weaver#copy running-config startup-config
    Destination filename [startup-config]?

    how to copy the file !!!please help

  28. xallax
    October 6th, 2011

    @tornado
    press Enter or write the desired destination file name

  29. Bala
    October 9th, 2011

    Do we need not bind the access list to any interface while using it for NAT over load? In the above example, they haven’t done any binding of the access list to any interface. Kindly confirm

  30. 518
    October 10th, 2011

    @ MARK: Thanks, it worked. Default route on “Weaver” RTR is needed and just had to configure another 2811 with static route.

    @ MAS: You may want to configure another 2811 since the “cisco” password is not valid on ISP router.

    -518

  31. Koffy
    October 11th, 2011

    @xallax
    I need your help, if you have the time.
    The question comes with a diagram, but since I can’t bring up the diagram, I’m going to write it out in the best way I can.

    Host A, a PC has IP address 10.1.1.2 is connceted via Fa0/0 interface to a router R1. R1 Fa0/0 IP address is 10.1.1.1. R1 Se0/0 is connected to router R2 Se0/0. R1 Se0/0 IP address is 172.30.20.1. R2 Se0/0 has IP address 172.30.20.2. A Web server is connected via Fa0/0 interface to router R2. Web server IP address is 192.168.1.2. R2 Fa0/0 has IP address 192.168.1.1

    Question read: R1 is performing NAT for the 10.1.1.0/24 network, and R2 is performing NAT for the 192.168.1.2/24 network. What would be valid destination IP address for Host A to put in its IP header when communicating with the Web server?

    1. 10.1.1.1
    2. 172.30.20.2
    3. 192.168.1.2
    4. 255.255.255.255

    It will be helpful if the answer comes with some explanations. Thanks.

  32. DimS
    October 12th, 2011

    @Kofty: Strange question.
    1. Incorrect. It’s IP address of F0/0 R1 but we need to connect to WEB server.
    2. Incorrect. It’s IP address of S0/0 R2.
    3. Correct. It’s IP address of WEB server.
    4. Incorrect. It’s broadcast address and it has no use in the unicast packet.

    Where is NAT here? I don’t see it.

  33. Koffy
    October 12th, 2011

    @DimS
    Maybe the question is misleading without the diagram. I am going try to recreate it the best way I can.

    The diagram has A PC Host A. This PC is connected to router R1. R1 has a serial connection to a router R2(serially). A Web server is connected to the router R2. Between the PC and R1 is Fa0/0 connection. The two routers has serial connection (R1Se0/0, R2 Se0/0). Between the Web server and R2 is a Fa0/0 connection. (R1Fa0/0 is the gateway to the PC, and R2Fa0/0 is the gateway to the Web server)

    Now the IP addresses assignment: PC has IP add. 10.1.1.2, R1 Fa0/0 has IP add. 10.1.1.1, R1 Se0/0 has IP add. 172.30.20.1. R2 Se0/0 has IP add. 172.30.20.2, R2 Fa0/0 has IP add. 192.168.1.1, Web server has IP add. 192.168.1.2

    The question reads: R1 is performing NAT for the 10.1.1.0/24 network. And R2 is performing NAT for the 192.168.1.0/24 network. What would be valid destination IP address for Host A (PC) to put in its IP header when communicating with the Web server.

    A. 10.1.1.1 B. 172.30.20.2 C. 192.168.1.2 D. 255.255.255.255

    Actually the asnwer is B. I just needed a second opinion with some explanation. I believe the question is more focus on PC and its IP header. Any one with some opinion is welcome. Thans.

  34. xallax
    October 12th, 2011

    @koffy
    please upload the pic to imageshack or similar and post a link to it next time, it would be far easier to get an answer :)

  35. Koffy
    October 12th, 2011

    @xallax
    Thanks. I will do that next time.

  36. Diego
    October 14th, 2011

    Guy i take ccna soon but diarrea all over and quick tell me how to ccna in 3 hours. faster i exam and diarrea

  37. Bunso
    October 17th, 2011

    @ all
    How would you enter this on the access-list 1 if you have 254 host 192.168.6.1 192.168.6.254?

    access-list 1 192.168.6.0 0.0.0.254
    Is this right?

    Thanks,

  38. Bunso
    October 17th, 2011

    Sorry what I mean is this.

    access-list 1 permit 192.168.6.0 0.0.0.254

    I’m confuse on the wild card mask…

    Thanks again,

  39. xallax
    October 17th, 2011

    @bunso
    so…
    wildcards are the opposite of subnets.
    you can’t use wildcard at random.

    for a subnet of 255.255.255.128 the wildcard would be….
    255.255.255.255 -
    255.255.255.128
    ______________
    000.000.000.127

    for a subnet of 255.224.0.0 it would be 0.31.255.255
    for a subnet of 255.255.192.0 it would be 0.0.63.255 and so on

    now… you gave us these pieces of information:
    network: 192.168.6.0
    number of hosts: 254
    well… you would have a problem using exactly 254 hosts + 1 router interface as default gateway on a single class C network… the IPs wouldn’t suffice.

    anyway, to answer your question i have to ask you this: what is the best subnet mask to use for 254 hosts on the 192.168.6.0 network?
    answer: 255.255.255.0 (/24)

    knowing the subnet mask makes it easy to figure out what wildcard mask is needed on the ACL.

    255.255.255.255 -
    255.255.255.0
    ______________
    000.000.000.255

    that is 0.0.0.255

    your ACL line would be “permit 192.168.6.0 _ 0.0.0.255″

  40. Bunso
    October 17th, 2011

    @xallax
    On the problem above regarding NAT Sim it should be like this right
    Router1(config)#access-list 1 permit 192.168.6.64 0.0.0.64
    not .63
    in my case as you said this would be right
    Access-list 1 permit 192.68.6.0 0.0.0.255
    not .254

    This access list will be input in the Nat pool problem.

    Thanks,

  41. Bunso
    October 17th, 2011

    Oh yeah this is one of the question on my CCNA test last friday which i failed 815 score. That why im asking, it called for 254 clients that need to access the internet simultaneously.

    The rest of the number on the sim problem above are the same except for the client.

    So this what I put on the access list
    access-list permit 192.168.6.0 0.0.0.254

    which i’m not sure about.
    Thanks,

  42. confusion
    October 19th, 2011

    @bunso, ei let me share my idea about this “wild card bits” cause i think you only making it harder for you. actually wild card bit is just the reverse of the subnet mask… so in short if you’re given a subnet mask of 255.255.255.0 its wild card mask is 0.0.0.255 . to make it more simpler rather than the use of binary bit just subtract the given subnet mask to 255.255.255.255. example 62 users were i think the subnet mask should be 255.255.255.192 or /26 then just do this 255.255.255.255 – 255.255.255.192 = 0.0.0.63 . . . hope it lighten up even a little…

  43. confusion
    October 19th, 2011

    and for your CCNA situation should’ve use wild card bits of 0.0.0.255 . always remember your VLSM to make it easier…

  44. Anonymous
    October 24th, 2011

    @Bunso

    Am assuming the mask is /24 which is 2^8=256(254 clients to access internet simultaneously)
    Therefore inside local address is 192.168.6.0/24…..255.255.255.128
    access-list 1 permit 192.168.6.127 0.0.0.126
    Mathematically:lets focus on the forth octet……127+126=253, this will allow 254 client to access internet simultaneously…..0 to 253 equals 254
    ip nat inside source list 1 pool mypool overload
    This will instruct NAT to map ACL 1 to the pool (inside global addresses)
    Remember to use the word “OVERLOAD” at the end of. the instruction.
    Frankly, this is a very tight scenario for a Class C network….(127 is broadcast address)
    Any suggestion from anyone? Thanks.

  45. Newbie
    October 26th, 2011

    @all

    Ip range 10.0.0.16 – 10.0.0.20

    Hey can u tell me the wildcard address of this ip range

    I guess it should be 0.0.0.7

  46. Koffy
    October 27th, 2011

    @Newbie

    Am guessing this is a /28
    10.0.0.16-10.0.0.20…….255.255.255.240……0.0.0.15

    I hope am right. Any ideas?

  47. John
    October 27th, 2011

    So while most people have been getting VTP, ACL2, and EIGRP sims, NAT is still a possibility? Who had NAT come up?

  48. Anonymous
    October 28th, 2011

    @Newbie

    Ip range 10.0.0.16 – 10.0.0.20

    Hey can u tell me the wildcard address of this ip range

    I guess it should be 0.0.0.7

    It is correct, subnet no’s, 8, 16, 24 etc..increment of 8, so wildcard mask is 0.0.0.7.

  49. Parvez Alam
    October 28th, 2011

    hey
    plz help with latest new n dumps my exam held on after eid 2011 plz plz plz
    parvezcs@yahoo.com
    Regards.

  50. Koffy
    October 30th, 2011

    @xallax
    This question came up on share your ccna experience. I tried explaining it, but am not sure if I was on the right track. Can you please help. Thanks.

    please anyone can xplain…thanks

    Refer to the exibit. Which command would allow the translations to be created on the router?

    Router#show ip nat translations

    ip nat pool mynats 1.1.128.1 1.1.135.254 prefix-length 19 — acme answer

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