ang3lus

asked on

# subnetting and mask

Hi

if i given network address, number of subnet and number of hosts ?

how i can find new network mask ?

please provide explain with example

thanks in advanced

if i given network address, number of subnet and number of hosts ?

how i can find new network mask ?

please provide explain with example

thanks in advanced

ASKER

i want to understand mathematical operations

i already check this site

i already check this site

Here is a good start for understanding the math involved:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

ASKER CERTIFIED SOLUTION

membership

Create a free account to see this answer

Signing up is free and takes 30 seconds.

**No credit card required.**
If you want. Pull up the basic Windows calculator. Change it to scientific view (programmer in Vista/7) and use the BIN and DEC radio buttons to type numbers in binary and convert them to decimal.

ASKER

for example

if the network address is 156.233.0.0

after subnetting there is 126 subnets and 500 hosts in each subnet.

after done some mathematical calculation to calculate new mask

i got :

255.255.255.0

am i correct ?

if the network address is 156.233.0.0

after subnetting there is 126 subnets and 500 hosts in each subnet.

after done some mathematical calculation to calculate new mask

i got :

255.255.255.0

am i correct ?

Not quite. You have a /24 subnet here, meaning 8 bits left for the host part. That means 2^8 256 addresses in a subnet: 156.233.0.0-156.233.0.255

Try it the other way around. You want 500 hosts in a subnet. Then you'll need atleast 2^9 = 512 addresses in the subnet, so 9 bits. That leaves 23 bits for the mask so well get 255.255.254.0 as a subnet mask (156.233.0.0-156.233.1.255). And 128 subnets for that matter.

Try it the other way around. You want 500 hosts in a subnet. Then you'll need atleast 2^9 = 512 addresses in the subnet, so 9 bits. That leaves 23 bits for the mask so well get 255.255.254.0 as a subnet mask (156.233.0.0-156.233.1.255

http://www.subnet-calculator.com/