16 Replies to “How IP Addresses Work

  1. Question 1 in the video
    You say that for class a= there are 128 host networks.
    The value of 7bits =1111111=64+32+16+8+4+2+1=127
    Or do i need to count the 0 as a 1 cause with that i would get 128
    The formula for bit is actually 2^b
    When i do 2^7 i do get 128
    Why is that?

  2. The 255.255.0.0 subnet mask has 16 bits turned on. The 255.255.240.0 subnet mask has 20 bits turned on. That’s an additional four bits for subnets.

    The 16bits that are turned on come from the first two 255.255 right.
    What’s the math behind 255.255.240.0 has 20bits turned on? I can understand that 4 bits subnet is 16. But the rest i cannot

    1. I think i got part of the answer 255.255.240.0 has 20 bits cause the first two 255.255. Can fit in the whole 8bit so thats 16. 240 can fit in 128, 240-128=112,
      112 -64= 48, 48-32=16, 16-16=0. I have used 4 of the 8 bits right? 16+4=20 bits used for the subnet. Now if i want to convert bits to decimal we go from right to left. That means that 4 bits fits into
      2^4=16 so there are 16 subnets.
      From the total 32bits we used 20 bits. That means there are still 12 bits left for the host. 2^12=4096 host

  3. In the video 12:16
    You say devices in the same subnet must be in the same ip network
    If not they cannot communicate
    And if they are on the same ip network, but seperated by a router they are also not able to communicate.

    Isn’t that the whole reason why in quiz 4 they are not able to communicate?

    1. Because the router is being cut to only have 4 hosts on the network. It cannot connect to the other hosts that are outside of its range. So the middle cannot connect to the right,but the left one can connect to the middle. Still without succes to reaching the right. I am correct?

    2. Yes, in quiz 4, the routers should be in the same subnet (a /30 in this example), but they are not.
      As they’re not in the same subnet, they cannot communicate with each other, which is why the network on the left cannot communicate with the network on the right.

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