Regarding to Subnetting


Let’s assume N/W is

Suppose,on the first time, a company want to give 50 ip to employees. so network engineer can use a N/W
After some time of period company need 100 ip and want to use remaining ip address.
Then, what do network engineer?



Here you have to do VLSM SUBNETTING
first block will have 64 ip
Subnet mask will be
62 valid ip can be used from this network
Plan accordingly.
First block valid ip
Second block will have 128 ip address
Subnet mask will be
Valid up range will be



By this method if i want to give ip address to int0/1 to router the it will over lapped with int0/0.



Hi Praven,
if you apply VLSM you must respect the addresses range from 0 to 255
You have to split the entire address space 256 in smaller spaces.

| 64 | 64|
| 128 |

So, if you take the first range x.x.x.1 --> x.x.x.63 you can’t apply the next range x.x.x.65 --> x.x.x.191 because you overlap the next 64 addresses
you have to put it aside the next available block 64 address x.x.x.65 -->x.x.x.126 (which you can further split in the future) and begin from x.x.x.128 --> x.x.x.255
in this way there will not be overlapping. Following my router configuration:

interface FastEthernet0/0
ip address (first block 62 ip address)
interface FastEthernet0/1
ip address (second block 126 ip address from 129 to 254 without overlap)

Here you can split the 64 available adresses from x.x.x.65 --> x.x.x.126 in two block of 32
with a mask /27
interface FastEthernet0/2
ip address
interface FastEthernet0/3
ip address