Netmask madness

[steve]

I'm taking a course on Networking.
I'm confused by a lot of things but here is the latest confusion.

I have been going on the net to find questions regarding subnettting and
trying to practice.

One question says which one of the following subnet masks offer 155 usable
subnets and minimum of 192 usable hosts. You have been assigned an ip of
128.167.0.0

Assuming that 2^Subnet Bits -2 = # of subnets and 2^hostbits -2 = hosts

The masks I'm offered are.

255.255.254.0
255.255.0.0
255.254.0.0
255.255.255.0

Despite my reading Im confused where I should count my bits from to be used
in my calculations.
The first gives me 7 Sub bits and 9 host bits. that's not enough.

But im not sure what number to use in the second case eg 255.255.0.0 to do
my calculation,

The third number I think is wrong because it's a class A network, so it
wount work at all.

And the third, well Im not sure but it looks like it should be for a class C
network.

Im assuming that the Ip 128.167.0.0 is a class b network.

Anyway you can see I'm confused.

Can anyone provide some insight in helping me. I guess Im basically confused
on where Im to get the bits from (which octet) to calculate my subnets and
hosts. (among other things)

Thanks.

[Tony]

Try one of the free subnet calculators (Solarwinds do a good one) &
have a play with it. They will give you a visual representation of
what is happening, great if this is your learning style. Simply put
the numbers in & play around.
Enjoy

[Peter]

you need to determine how many host bits are required for min 192 host which
is 8 because 2^8 = 256 hosts.

Then you need 7 bits set to 1 added to the default mask (because 2^7=192) to
create the subnet mask so the only subnet mask that satisfies this is
255.255.254.0 in binary 11111111.11111111.(1111111)0.00000000 ones in
brackets, so the default mask for class B is 255.255.0.0 so you add 7*1's to
the 3rd octet which leaves 9 bits for the hosts more than enough for a
minimum of 192 hosts.

I hope this is clear enough for you.

Pete

"steve" <steve...@abc.com> wrote in message
news:i2a31e$n6d$2...@news.eternal-september.org...

[JanD]

Hi,

if you are into networking then this may be very handy
Subnet the Easy and Fast way CCNA ICND CCENT
http://www.youtube.com/watch?v=ugANqQprJFI&feature=related
If you look around more closely you'll find a lot that can be of interest
during your study.

bye,
JanD

"steve" <steve...@abc.com> schreef in bericht
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