VLAN ID Planner
Allocate 802.1Q VLAN IDs across sites in aligned blocks and check the plan fits the 4094 usable IDs.
Inputs
Total VLAN IDs Consumed
384
Aligned Block per Site
32IDs
Sites the ID Space Supports
124
Last VLAN ID Used
484
802.1Q ID Space Used
9.38%
Verdict
Fits — 3610 IDs spare
Step by step
Values used
Sites to number = 12 sites; VLANs needed per site = 20 VLANs; IDs reserved for infrastructure = 100 IDs; First allocatable VLAN ID = 101
VLAN ID
Each site gets the next power of two above its VLAN count so blocks stay bit-aligned; total = sites × block size, against the 4094 usable IDs.
Total VLAN IDs Consumed
= 384
Aligned Block per Site
= 32 IDs
Sites the ID Space Supports
= 124
Last VLAN ID Used
= 484
802.1Q ID Space Used
= 9.38
Verdict
= Fits — 3610 IDs spare
How it works
Rounding each site's allocation up to a power of two keeps VLAN ranges aligned, so a site's VLANs can be summarised in a trunk allowed-list or matched by a single mask instead of an arbitrary range. The planner then checks the total against the 4094 IDs 802.1Q actually gives you. VLAN IDs are a 12-bit field with no way to extend it, so a numbering scheme that is not aligned and bounded from day one turns into a renumbering project the first time you add a site.
Formula
VLAN ID
Each site gets the next power of two above its VLAN count so blocks stay bit-aligned; total = sites × block size, against the 4094 usable IDs.
- 4094
- 802.1Q usable VLAN IDs — 0 and 4095 are reserved by the standard
- block size
- 2^ceil(log2(VLANs per site))
- available
- 4094 minus the IDs you hold back for infrastructure
Frequently Asked Questions
How is VLAN ID calculated?
Each site gets the next power of two above its VLAN count so blocks stay bit-aligned; total = sites × block size, against the 4094 usable IDs. Rounding each site's allocation up to a power of two keeps VLAN ranges aligned, so a site's VLANs can be summarised in a trunk allowed-list or matched by a single mask instead of an arbitrary range. The planner then checks the total against the 4094 IDs 802.1Q actually gives you.
Why does VLAN ID matter?
VLAN IDs are a 12-bit field with no way to extend it, so a numbering scheme that is not aligned and bounded from day one turns into a renumbering project the first time you add a site.
What values do I need to enter?
This calculator takes 4 inputs: Sites to number, VLANs needed per site, IDs reserved for infrastructure, First allocatable VLAN ID. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
What happens when 4094 VLANs is not enough?
You move the scaling boundary above 802.1Q: QinQ (802.1ad) gives a second 12-bit tag, and VXLAN's 24-bit VNI gives roughly 16 million segments. Both keep VLAN IDs local to a switch or site rather than globally unique.