Free Subnetting Lesson - 2
Subnetting Lesson 2
How did you get along with writing out the
Subnetting Secrets Cheat
Sheet? It should only take a few goes to be able to write it
out from
memory. That is actually the question half answered already
would you
believe.
Now we need to know how to actually use the chart to answer a
subnetting
question. We will start with a nice easy one for you and one
that is
very typical for exams or job interviews:
Which subnet is host 192.168.1.57/29 in?
Step 1 - we need to determine what subnet mask the /29
actually looks
like when written out in full. The abbreviation /29 is known
as CIDR
or classless inter domain routing and is just a nice and quick way
of
writing a subnet mask out in shorthand.
We know from the binary page on subnetting secrets that subnet masks
are actually four lots of 8 binary bits so we can start to write out
the subnet mask as:
255 (8 bits). 255 (16 bits). 255 (24 bits). We have 24 bits
with the
subnet mask 255.255.255 and we need to add 5 to get to 29. Go
to
the subnetting cheat sheet and tick down 5 places on the upper left
column.
| 128 |
 |
| 192 |
|
| 224 |
|
| 240 |
|
| 248 |
|
| 252 |
|
| 254 |
|
| 255 |
|
We can see that the last octet where 5 bits have been stolen to make
subnets from is 248 so the subnet mask is 255.255.255.248.
Step 2 - now tick the same amount along the top row to reveal
the
increments our subnets will be going up in.
Our subnets are going up in increments of 8. We are looking
for
host number 57 which is in the fourth octet. We know the host
number is in the fourth octet for two reasons. Firstly the
network
number starts with 192 so it is Class C which means the host is
always going to be in the last octet. We can also see that we
are
stealing bits from the fourth octet because it has 248 in the mask.
Step 3 - write out your subnets until you reach the one host
number 57 is in:
192.168.1.0 not in here so add 8
192.168.1.8 not in here so add 8
192.168.1.16 not in here so add 8
192.168.1.24 not in here so add 8
192.168.1.32 not in here so add 8
192.168.1.40 not in here so add 8
192.168.1.48 not in here so add 8
192.168.1.56 our host is in this subnet
192.168.1.64
We have our answer. Host 192.168.1.57/29 is in subnet
192.168.1.56
That is enough for today. If it hasn't made sense
yet then please be patient with yourself and review this example
again.
If you really want to be a subnetting master then please rush over
to the below url and invest a few bucks in Subnetting Secrets
e-books
and videos. You will save yourself weeks of wasted time and
effort
studying other subnetting resources which only serve to confuse the
readers.
http://www.subnetting-secrets.com/buy_subnetting_secrets.html
Or it is given away to all members of
http://www.howtonetwork.net which is a unique Cisco
CCNA online
training site I have created.
Until tomorrow
Or call us on the toll free numbers at the top.
|
