Always design your subnets from the . VLSM Practice Scenario Allocate the block 172.16.0.0/24 for: HR Department: 100 hosts Sales Department: 50 hosts IT Department: 20 hosts Router Link: 2 hosts Execution: HR (100 hosts): Requires a /25 mask ( Range: 172.16.0.0 to 172.16.0.127 Sales (50 hosts): Requires a /26 mask ( Range: 172.16.0.128 to 172.16.0.191 IT (20 hosts): Requires a /27 mask ( Range: 172.16.0.192 to 172.16.0.223 Router Link (2 hosts): Requires a /30 mask ( Range: 172.16.0.224 to 172.16.0.227 Cheat Sheet for Guru Speed CIDR Prefix Subnet Mask Value (Last Octet) Block Size (Magic Number) Total Usable Hosts /25 .128 /26 .192 /27 .224 /28 .240 /29 .248 /30 .252
Subtract the interesting octet value from 256. Calculate Total Subnets: 2n2 to the n-th power is the number of borrowed bits). Calculate Total Hosts per Subnet: is the remaining host bits). ip subnetting from zero to guru pdf
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