Who Likes Cake? VLSM? •Get maximum usage from your addresses •192.168.1.0/24 = 1 network – 254...
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Transcript of Who Likes Cake? VLSM? •Get maximum usage from your addresses •192.168.1.0/24 = 1 network – 254...
In 60 Days - CCENT
VLSM
Who Likes Cake?
We Eat Cake by the Slice
VLSM
• Variable length subnet masking
• Cuts your network into slices
Why VLSM?
• Get maximum usage from your addresses
• 192.168.1.0/24 = 1 network – 254 hosts
• 192.168.1.0/26 = 4 subnets – 62 hosts
• 192.168.1.0/28 = 16 subnets – 14 hosts
Using VLSM
• Work out your subnet/host requirements
• Use the Subnetting Secrets lower chart
1 2 4 8 16 32 64 128
128
192
+ + + + + + +
224
240
248
252
254
255
2-2
4
8
16
32
64
128
256
512
BITS 128 64 32 16 8 4 2 1
Subnets
128
192
224
240
248
252
254
255
2-2
4
8
16
For working out which subnet a host is in
For working out how many subnets and hosts per subnet
BITS 128 64 32 16 8 4 2 1
Subnets
128
192
224
240
248
252
254
255 Subnets Hosts
2-2
4
8
16
32
64
4 subnets 64-2 so 62 hosts per subnet
Subnets Hosts
2-2
4
8
16
32
64
128
256
512
1024
2048
Example – 172.16.0.0 We need 60 subnets & 1000 hosts per subnet
BITS 128 64 32 16 8 4 2 1
Subnets
128
192
224
240
248
252
254
255
2-2
4
8
16
We have stolen 6 bits so mask is /22 (16+6) or 255.255.252.0
Slicing Your Network
• VLSM lets you slice your subnets further
Slicing Down
• Take network 192.168.1.0 / 24
• 1 network with 254 hosts
Change to 192.168.1.0/26
192.168.1.0/26 Subnet Hosts
192.168.1.0 1 62 hosts
192.168.1.64 2 62 hosts
192.168.1.128 3 62 hosts
192.168.1.192 4 62 hosts
What If?
• You have 2 smaller subnets
• Each requires 30 host addresses?
Change to 192.168.1.0/26
192.168.1.0/26 Subnet
192.168.1.0 1 62 hosts
192.168.1.64 2 62 hosts
192.168.1.128 3 62 hosts
192.168.1.192 4 62 hosts
Change to 192.168.1.0/27
192.168.1.0/27 Subnet
192.168.1.0 1 30 hosts
192.168.1.32 2 30 hosts
192.168.1.64 Can’t Use
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