What is VLSM? how to Calculate VLSM? where it is use and
why?

Answer Posted / hargie

VLSM (variable length subnet mask) is ipv6 classless ip
addressing. Use to subnet an already subnettted ip adress.

how to calculate vlsm?

first if you have a topology you must determine which
network have the greatest number of host. then assign it as
the first subnet.

ex: ISP wan = 20 Host
IP AD=192.168.1.0

Second you must have a knowledge about octet table...


octet table

1 2 3 4 5 6 7 8 1stoctet
9 10 11 12 13 14 15 16 2ndoctet
17 18 19 20 21 22 23 24 3rdoctet
25 26 27 28 29 30 31 32 4thoctet
128 64 32 16 8 4 2 1 delta
128 192 224 240 248 252 254 255 SUBNET
- MASK

USING octet table u can determine the usable ip adresses.

isp wan have a 20 host so its means
20host delta=32 subnet mask=255.255.255.224

ADD THE DELTA=32 IN THE IP ADRESS :
192.168.1.0
+ 64
------------
192.168.1.64
configuration:
192.168.1.0/27

192.168.1.0/27-NEtwork address
192.168.1.1/27-1ST USABLE IP ADDRESS
.2/27-2ND USABLE ADDRESS

.62/27-LAST USABLE IP ADRESS
BEFORE THE 192.168.1.64, 192.168.1.63 IS THE BROADACST ADRESS.
SO,
192.168.1.63/27-BROADCAST ADRESS
THEN
192.168.1.64.0 IS A NEW IP ADRESS, BUT WE DON'T NEED THIS!!!
SO FROM 192.168.1.1 TO 192.168.1.62, YOU CAN GET ANY IP
ADRESSES FROM THAT,

OK

Is This Answer Correct ?    29 Yes 16 No



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