Question on Subnetting

[xx1111xx]

Hi, I have a question about subnetting on the Network+ exam. Do the questions ask something like,The Subnet Training Guide what subnet does 172.16.116.4/19 sit on, or are they definition questions. Do I need to know subnetting for the exam?
Thanks Much!

[eduromer]

Originally Posted by xx1111xx

Hi, I have a question about subnetting on the Network+ exam. Do the questions ask something like,The Subnet Training Guide what subnet does 172.16.116.4/19 sit on, or are they definition questions. Do I need to know subnetting for the exam?
Thanks Much!

if you are on the networking track, you need to know subnetting period, dont try to skipp it

[Rootstonian]

Agreed...IPv4 addressing is very important. And in your example above, you'll want to be able to identify the Network ID and Host ID.

Now, I'm pretty new to this myself, but I know /19 = 255.255.224.0 subnet mask. From there, it's some binary conversion to get your ID's (since 19 is not divisible by 8 ).

It's called "variable length subnet masking". According to MS Press book for 70-642, the authors state that is is probably the toughest question you'll face on that exam

The concept is easy to understand: You have 3 buildings with 250, 50 and 10 computers respectively. You're not going to get an address block from the WAN folks that let you have a nice easy subnet mask of 255.255.255.0 that gives you 254 hosts...that's a waste of address block space for the 50 host and 10 host buildings. The WAN group will give you at least 310 addresses; you'll have to use variable length subnetting

[Psoasman]

You mainly need to know the Classes A, B, C, the ranges each class has, APIPA, Private ranges, know how to recognize a MAC address. You should know your subnet masks, but I don't recall a lot of subnetting problems on this exam, you will see them on the 291 or in the CCNA.

[captobvious]

Subnetting Made Easy

[SysAdmin4066]

I'm always amazed at the network engineers who dont know how to subnet. Subnetting is definitely a necessary tool to put in your toolbox, regardless of whether it's on this exam. I havent taken the CCNA in quite some time, but I remember that was pretty heavy there. I would imagine any exam certifying true network proficiency should require some actual subnetting examples. As in your question example.

[AHMAD HABU]

Hi, I
about class B questions 172.16.116.4/19 255.255.224.0, 256-240=16 the block size of /19 is 16
0,16,32,48,64,80,96,102.128.144,150,166

[earweed]

If you're on ANY network track you should go ahead and learn subnetting now. You wont see much of it on this exam, but you'll definitely see it later.
The Net+ is a pretty broad exam. You probably wont see a block size or need to calculate no. of hosts for a certain subnet but it is in the objectives.

[SephStorm]

Since when is subnetting on net+?! I probably wouldn't have made it if it was there when I went through!

No, have faith. VLSM is... difficult, but it can be done. the issue is the way the question will be formatted, at least in cisco exams...

[barekman6661]

all you have to remember is that ipv4 has 32 bits. a has 8 b has 16 and c has 24 . for a point to point network always use a /30 and to max subnets use the max amount of subnet bits you can use, and to max host use the most host bits you can.

[jamesleecoleman]

Originally Posted by SysAdmin4066

I'm always amazed at the network engineers who dont know how to subnet. Subnetting is definitely a necessary tool to put in your toolbox, regardless of whether it's on this exam. I havent taken the CCNA in quite some time, but I remember that was pretty heavy there. I would imagine any exam certifying true network proficiency should require some actual subnetting examples. As in your question example.

I am really surprised that some network engineers make that that far without knowing how to subnet. I guess its a good thing that there are subnet calculators to help cover their back.

[xineo]

subnets with /(number) is called a CIDR don't sweat them too much they arent hard to understand.

if you have a 172.1.1.10/18

Knowing thats a B subnet by looking at the 172 you know the first two parts of the subnet will be a 255.255.x.x

I simple way to determine the next number for the subnet is taking the (2) 255's and subtracting them from the cidr.

What i mean by this is that the (2) 255's is nothing more than 2 sets of 8 bits turn on (means there 1's not 0's in binary)

so in binary it looks like this 11111111.11111111.x.x

Knowing that all you have to do is count up the 1's which equals 16.

Now take that 16 and subtract it from the CIDR which was 18 (look at the IP) now you get the number 2.

So what does the number 2 thats left over mean?

Since earlier we had 11111111.11111111.x.x
we take that 2 and turn it into two bits (meaning 11)

so now the subnet in binary is 11111111.11111111.11.x

since now all we have to do is turn them into numbers. since [8] 1's is 255

then the first two numbers is 255.255 (ya im repeating myself lol)

now in binary the numbers go as the following 128,64,32,16,8,4,2,1 (Helpful Tip:For sub netting We read binary from right to left)

since we only have (2) bits left and since they fall under 128 and 64 we simply add 128 and 64 together and we get our subnet

so now your subnet with the cidr 18 is 255.255.192.0

hope that clarifies and didnt confuse you

[burner27]

Originally Posted by AHMAD HABU

Hi, I
about class B questions 172.16.116.4/19 255.255.224.0, 256-240=16 the block size of /19 is 16
0,16,32,48,64,80,96,102.128.144,150,166

I believe the block size is 32.

/19 = 224

256-224=32

and the host is on the 172.16.96.0 network

Did i do the math right?

[Devilsbane]

You will need to know subnetting. And you are going to need it in nearly everything you do, so pick it up now. It isn't that difficult, just takes time to comprehend whats going on. Once you got it, you got it. It will just click one day.