Subnetting help

Hello, I have some subnetting questions. I am not sure where to begin with these problems. After trying to study for over 6 hours I figured I would come here for some help.

I need to take 139.68.0.0/16 and subnet it into two subnets (subnet1, subnet2) of the same size. I need to find the first and last network and broadcast address for the blocks.

I then need to take subnet1 and allocate 64 blocks of 512 IP addresses. Subnet2 needs 128 blocks of 256 IP addresses. I need to find the first and last network and broadcast address for the blocks.

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Comments

sratakhin

Your two subnets will have thew following addresses:
139.68.0.0/17
139.68.128.0/17

Thus, the first network in the first subnet will be 139.68.0.0/23 with the broadcast 139.68.1.255
The last network in the first subnet will be 139.68.126.0/23 with the broadcast 139.68.127.255

The first network in the second subnet will be 139.68.128.0/24 with the broadcast 139.68.128.255 (that was easy)
And the last network will be 139.68.255.0/24 with the broadcast 139.68.255.255

No binary stuff, figured it out while I was typing.

shatteredzman

Thank you.
Okay so I am a bit relieved, I got the first two ip addresses correct.

Okay now I need to allocate 128 blocks of 256 ip addresses in the 139.168.126.0/24 address. Like before I need to find the first and last network and broadcast address and network address for the blocks.

I really hate to be a bother, but could you explain how you got these answers? This is the first of a couple assignments I will have over this. If I don't know how to do this now, I won't be able to figure it out on my own.

sratakhin

You cannot allocate 128 blocks of 256 IP addresses in a class C network. You would have to use a /17 mask to do it.

I can't really explain the logic I use when I do subnetting. I practiced it a lot when I prepared for CCNA, so it's kind of obvious to me now.

shatteredzman

sratakhin wrote: »

You cannot allocate 128 blocks of 256 IP addresses in a class C network. You would have to use a /17 mask to do it.

I can't really explain the logic I use when I do subnetting. I practiced it a lot when I prepared for CCNA, so it's kind of obvious to me now.

Hmm you are right. I guess I misread the question. It says I need to use the last part of 139.68.128.0/17
I'm sorry if I seem clueless, but it is because I am clueless.