IP addressing/subnetting help

Discussion in 'OT Technology' started by Gadget, Jan 29, 2007.

  1. Gadget

    Gadget New Member

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    I'm having a hard time grasping the whole ip addressing and subnetting subject. Can anyone help walk me through this example?


    Given below is a network with two Ethernet segments connected by two routers. The IP address and subnetmask at each interface is provided. Due to problems in addressing there are problems in communication. Suggest a simple solution to address the problem. (Hint: work out range of IDs in the three subnets and look for overlaps)

    [​IMG]
     
  2. Darketernal

    Darketernal Watch: Aria The Origination =)

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    If you would take a scissor and cut the wire in the middle you would have two seperate and functional networks.

    They make you confused because they are putting two routers connected to eachother ,which basically means you have two networks connected to eachother, how does 1 network correctly work?

    -same subnet mask number
    -different ip adresses.

    The router is the devider ,lets say if the teacher is giving blue ribbons to 3 children of team 1, now if the other teacher also gives blue ribbons to her 3 children of team 2 then it makes no sense,because both teams have the same colour, when playing they cannot distinguish eachother because they are all from the same team.

    If one team is given red ribbons, and the other blue, then the teachers know who is playing in their team.

    This is why you can't have two of the same subnet masks of two routers connecting to eachother, one must be team blue, one must be team red. so the left part must have subnet 255.255.255.224 , and the right part must have 255.255.255.223

    So simply by letting one teacher distribute another colour of ribbons they can distinguish eachother, or in other words, the simple solution is to change one subnet in the router, and the teacher will start deviding a different colour to its children.


    Ip adresses are like the numbers of the children, like child 1 child 2 child 3, (computer 1 computer 2 computer 3) , each has its own name so you can distinguish them from eachother. So basically the router is the coach/teacher of a team of children(computers) If another teacher and team is added to the game ,then their team must wear a different type of colour.
     
    Last edited: Jan 29, 2007
  3. ShapeShifterz

    ShapeShifterz Longtime Lurker

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    Huh?

    The reason this doesn't work is because the interface that is assigned 10.1.1.100 falls outside of that ethernet's subnet range.

    There should be 3 subnets:
    10.1.1.32/27 Subnet A
    10.1.1.96/27 Transit Network
    10.1.1.192/27 Subnet B

    In this example, host 10.1.1.41 won't be able to reach its default gateway.
     
  4. johan

    johan Active Member

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    the host on the left, 10.1.1.41 is shown with a /27 mask

    This means that ip address is contained in the range 10.1.1.33 to 10.1.1.62

    The router interface for that segment is shown as 10.1.1.100
    So that host will not be able to reach that router interface, which presumably should be that host's default gateway, which means that host will not be able to communicate off its local ip range (.33 to .62), so it cant talk to the other host 10.1.1.200

    The router interface 10.1.1.100 is also shown with a /27 mask which means it participates in the 10.1.1.96 to 10.1.1.126 address range.

    This is the same range that its other interface participates in which doesn't make a whole lot of sense.

    Readdress the router int of 10.1.1.100 to something in the 10.1.1.33 to .62 range.

    Now the router addressing makes sense, and since the interface is now in the .33 to .62 range, that host will be able to use it to send off its local segment.
     
  5. Cthalupa

    Cthalupa New Member

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    Er, no. The subnet mask just determines the logical address range.

    Say I have two routers connected with one serial interface - S0 on R1, and S1 on R2.
    I give the R1S0 interface the ip 192.168.1.1 with a subnet mask of 255.255.255.252 and R2S1 192.168.1.2 with a subnet mask of 255.255.255.252.

    255.255.255.252 is not a subnet - it's a subnet mask. The subnet is the 192.168.1.0 - 192.168.1.4 IP range.

    Things get a bit more complicated when you throw in CIDR and VLSM, but those are still simple after the initial first reaction to them.


    http://www.ralphb.net/IPSubnet/ has an in depth tutorial on subnetting. Worth taking a look at. I also suggest you get a strong command of binary to decimal conversion, as that is a huge part of subnetting.
     
  6. johan

    johan Active Member

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    If you cut the network in the middle you would not have two functional networks.
    Host on the left cannot reach the left router.
     

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