CCNA 200-301 v1.1 reference — Network Fundamentals

VLSM planning

Allocate variable-length subnets inside a parent block without overlap, verify capacity and alignment, and keep space for growth.

Objective 1.6v1.1 exam target

Sort the subnet requirements by host count, largest first.
For each need, pick the smallest prefix whose usable capacity covers the hosts.
Allocate the next free aligned block — the network address must be a multiple of the block size.
Track used space and remaining free space; leave headroom for growth.
Verify every allocation: aligned, contained in the parent, non-overlapping, sufficient.

Allocating largest-first keeps blocks contiguous and leaves room to grow.
Hosts needed	Smallest prefix	Usable capacity	Addresses used
1	/32 or /31 p2p	1 / 2	1 / 2
2	/30	2	4
3–6	/29	6	8
7–14	/28	14	16
15–30	/27	30	32
31–62	/26	62	64
63–126	/25	126	128
127–254	/24	254	256

Allocating largest-first keeps blocks contiguous and leaves room to grow.

Alignment: the network address must be a multiple of the block size — 192.168.10.64/26 is valid, 192.168.10.96/26 is not (96 is not a multiple of 64).
Containment: every allocation must fit inside the parent block.
Non-overlap: no address may appear in two allocations.
Capacity: usable hosts ≥ required hosts, or the allocation fails at deploy time.

Carve 192.168.10.0/24 for four needs

Sort largest first: 90 → needs /25 (126 usable); 50 → /26 (62); 20 → /27 (30); 2 → /30 or /31.
Allocate /25 first: 192.168.10.0/25 → .0–.127 used, .128 free.
Allocate /26 next: 192.168.10.128/26 → .128–.191, next free .192.
Allocate /27: 192.168.10.192/27 → .192–.223, next free .224.
Allocate the WAN /30: 192.168.10.224/30 → .224–.227 (or /31 for a true point-to-point).

Result: .0/25 Sales, .128/26 Eng, .192/27 Ops, .224/30 WAN — non-overlapping, aligned, and .228–.255 still free.

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Targets CCNA 200-301 v1.1 objectives. Supplemental blocks are labeled beyond exam scope.