Divide 网络为 smaller subnets (VLSM)
变量 Length Subnet Masking (VLSM) divides 网络为 subnets 的不同 sizes, allocating address space 高效 based 开 need.
- 1
VLSM allows subnets 的不同 sizes 内相同父 网络. 为示例, /24 能够是 divided 为: one /25 (126 hosts), one /26 (62 hosts), two /27 (30 hosts 每个), 和 two /28 (14 hosts 每个). Allocate largest subnets 第一到 avoid fragmentation. 每个 subnet 必须是 aligned 到其 大小边界.
- 2 IP 信息查询器 →
Look 上每个 subnet 到验证其 范围不 overlap 具有其他. Enter 网络 address 和 prefix 为每个 subnet. tool shows address 范围 — 验证它们是 contiguous 和 non-overlapping.
- 3 高精度计算器 →
计算 subnet sizes: a /25 has 2^(32-25)-2 = 126 hosts, /26 has 62, /27 has 30, /28 has 14. Sum the sizes to verify they fit in the parent: 128+64+32+32+16+16 = 256 = /24. Plan allocations from largest to smallest to minimize wasted addresses.
常见问题
- 为什么 use VLSM 而非固定-大小 subnets?
- 固定-大小 subnets (FLSM) waste addresses — /24 为 point-to-point link wastes 252 addresses. VLSM allocates right-sized subnets: /30 为 point-to-point, /27 为小 office, /24 为大 department. 此能够保存 50%+ 的 address space.
- 如何 I align subnets?
- /26 必须启动在 address divisible 通过 64 ( 阻止大小). 192.168.1.0/26, 192.168.1.64/26, 192.168.1.128/26, 192.168.1.192/26 是有效. 192.168.1.32/26 是无效 — 它 crosses 192.168.1.64 边界. Calculate 阻止大小 as 2^(32-prefix) 和 align 到多个的 它.