1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Troubling questions

Discussion in 'Networks' started by kobem, Jun 8, 2009.

  1. kobem

    kobem Megabyte Poster

    791
    1
    50
    1- How is data transmitted across a network?
    Answer: using bits or using voltage pulses?


    2- when a packet traverses a network, what is never changed?

    a)source and destination IP
    b)source and destination MAC
     
    Certifications: CCNA
  2. greenbrucelee
    Highly Decorated Member Award

    greenbrucelee Zettabyte Poster

    14,283
    254
    329
    A:D because you can change a MAC with specialist tools
     
    Certifications: A+, N+, MCDST, Security+, 70-270
    WIP: 70-620 or 70-680?
  3. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92

    1) voltages are used to depict 1's and 0's?

    2) a) MAC's change every hop
     
    Certifications: CCENT, CCNA
    WIP: CCNP
  4. JonnyMX

    JonnyMX Petabyte Poster

    5,239
    211
    236
    1) Don't know. This networking stuff has always baffled me.

    2) Why would you want to change either?
     
    Certifications: MCT, MCTS, i-Net+, CIW CI, Prince2, MSP, MCSD
  5. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92

    I don't think he is referring to a manual change, more what happens as the packet goes from source to destination.
     
    Certifications: CCENT, CCNA
    WIP: CCNP
  6. greenbrucelee
    Highly Decorated Member Award

    greenbrucelee Zettabyte Poster

    14,283
    254
    329
    Oh I thought he meant manually, anyway I was still correct :D
     
    Certifications: A+, N+, MCDST, Security+, 70-270
    WIP: 70-620 or 70-680?
  7. UKDarkstar
    Honorary Member

    UKDarkstar Terabyte Poster

    3,477
    121
    184
    Depends, has it been filtered thru a router ? Where is the packet ultimately going ?

    Lots of variables..

    Is this for a course you're studying ?
     
    Certifications: BA (Hons), MBCS, CITP, MInstLM, ITIL v3 Fdn, PTLLS, CELTA
    WIP: CMALT (about to submit), DTLLS (on hold until 2012)
  8. kobem

    kobem Megabyte Poster

    791
    1
    50
    i found these questions in internetworking practice test site. Frame is handed down the physical
    layer while sending it and converted into bits. After this process it is transmitted
    so that answer has to be bits. Why not?

    for the second one : if a source host is behind NAT, private addresses are matched with public
    ones then we are able to go through Internet hence our source IP changes. When a transmission
    occurs between routers, does MAC change?
     
    Certifications: CCNA
  9. dmarsh

    dmarsh Terabyte Poster

    3,782
    302
    184
    Normally IP and MAC doesn't change. Of course there is NAT. And both IP and MAC addresses can be spoofed, so it really depends on the context of the question, its too general.

    Same with the first question. Bits have to be represented in the real world somehow, it could be pulses of electricity, pulses of light, it could be changes in an analog signal with FSK, again it all depends.

    Did you get your Masters ? What mark did you get ?
     
    Certifications: CITP, BSc, HND, SCJP, SCJD, SCWCD, SCBCD, SCEA, N+, Sec+, Proj+, Server+, Linux+, MCTS, MCPD, MCSA, MCITP, CCDH
  10. kobem

    kobem Megabyte Poster

    791
    1
    50
    answer of the second question has been given as "destination and source MAC. However,
    as i said above while doing NAT , our private IP replaced with public. In other words it changes
    with the router's IP.
     
    Certifications: CCNA
  11. dales

    dales Gigabyte Poster

    1,997
    46
    97
    question two though says when a packet traverses "a network" it does not say it crosses into different networks or even subnets so I would assume that it ment 2 computers attached to a hub or switch, and in that case the mac would no change.

    Voltage pulses are bits (or at least changes in voltages represent bits) so its kinda similar. but data is transmitted by voltages over the wire and the conditioning of the voltages equal the bits. Exactly the same way you could represent binary/bits on pretty much any format it you made a computer understand it (how about monkey (1). no monkey (0)) or Tea (1), Coffee (0).
     
    Certifications: vExpert 2014+2015+2016,VCP-DT,CCE-V, CCE-AD, CCP-AD, CCEE, CCAA XenApp, CCA Netscaler, XenApp 6.5, XenDesktop 5 & Xenserver 6,VCP3+5,VTSP,MCSA MCDST MCP A+ ITIL F
    WIP: Nothing
  12. kobem

    kobem Megabyte Poster

    791
    1
    50
    still doesn't understand the MAC or IP issue
     
    Certifications: CCNA
  13. Fergal1982

    Fergal1982 Petabyte Poster

    4,196
    171
    211
    Basically, depending on the circumstances, either, neither, or both could change.

    The devil is in the detail.
     
    Certifications: ITIL Foundation; MCTS: Visual Studio Team Foundation Server 2010, Administration
    WIP: None at present
  14. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92
    The question is basically assuming a more basic approach with no NAT.

    However, if you take NAT into consideration, when the packet leaves your NAT device, the source and dest IP will stay the same all the way to the destination. witht he MAC changing as it goes from device to device.
     
    Certifications: CCENT, CCNA
    WIP: CCNP
  15. dmarsh

    dmarsh Terabyte Poster

    3,782
    302
    184
    Well there is both src and dst IP and src and dst MAC in the packet. Does the destination MAC really change due to routing ?

    So how did the Masters go ? :D
     
    Certifications: CITP, BSc, HND, SCJP, SCJD, SCWCD, SCBCD, SCEA, N+, Sec+, Proj+, Server+, Linux+, MCTS, MCPD, MCSA, MCITP, CCDH
  16. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92
    MAC changes as it is used for sending packets locally.

    i.e. a switch has a MAC table, so when PC A sends a packet, presuming PC A already knows the MAC of the host it is sending to, it addresses it with the MAC address of the host, and sends it to the switch, which looks up it's MAC address table and forwards out the correct port. If the host is on a different subnet, it sends the packet with Source and destination IP of itself ande the host, but this time it puts the MAC of the defualt gateway.

    When that packet arrives at the default gateway, the DG will look up it's routing table figure out what interface to send the packet out, then strip out the source/detination MAC, and add the required data link headers ( for example, ethernet, meaning DG source MAC and next hop routers MAC as the destination)

    hopefully that makes some sense!
     
    Certifications: CCENT, CCNA
    WIP: CCNP
  17. kobem

    kobem Megabyte Poster

    791
    1
    50
    So you just say it by considering the man standing opposite of you knows as much as you- But details?


    you know, NAT built device provides matching your private IP with public IP. Isn't this a kind of
    change? Replacing?

    Assume another one : Packet is on the road by leaving the source host and passed one router (lets say miami) now is in internetwork. The next station is another router (lets say Kansas). There must be "data encapsulation" while sending and receiving between these two routers. Whatever, router .....

    to be continued
     
    Certifications: CCNA
  18. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92
    Yes, but for the purposes of this assume there is no NAT, as that is not what the question is getting at.
     
    Certifications: CCENT, CCNA
    WIP: CCNP
  19. kobem

    kobem Megabyte Poster

    791
    1
    50
    i do not understand something. We do not change source and destination IP address hence we have to
    reach the correct destination host somehow. But, MAC side?
     
    Certifications: CCNA
  20. danielno8

    danielno8 Gigabyte Poster

    1,305
    48
    92
    ^ whats your question about MAC side?
     
    Certifications: CCENT, CCNA
    WIP: CCNP

Share This Page

Loading...