VLAN Interface Calculator
Calculate VLAN tagging overhead and check VLAN ID capacity per interface (max 4094).
Inputs
VLAN IDs Remaining (of 4094 max)
4,082
802.1Q Tagging Overhead (Mbps)
1.6000
Tagged Frame Size (bytes)
1,504
Overhead as % of Frame
0.267%
Within VLAN ID Capacity?
true
Step by step
Values used
VLANs Needed on This Interface = 12; Untagged Frame Size (bytes) = 1,500; Frames per Second = 50,000
VLAN tagging overhead
tagged_frame_size = untagged_size + 4 bytes; max VLAN IDs = 4094
VLAN IDs Remaining (of 4094 max)
= 4,082
802.1Q Tagging Overhead (Mbps)
= 1.6000
Tagged Frame Size (bytes)
= 1,504
Overhead as % of Frame
= 0.267
Within VLAN ID Capacity?
= Yes
How it works
IEEE 802.1Q VLAN tagging inserts a 4-byte tag (2 bytes TPID + 2 bytes TCI, carrying the VLAN ID and priority bits) into each Ethernet frame, which adds a small but nonzero bandwidth cost proportional to frame rate — negligible for large frames but more noticeable for small, high-rate traffic. The 12-bit VLAN ID field theoretically allows 4096 values, but 0 (untagged/priority-only) and 4095 (reserved) are excluded, leaving a maximum of 4094 usable VLAN IDs per bridge domain — a hard ceiling relevant to large multi-tenant or service-provider deployments.
Formula
VLAN tagging overhead
tagged_frame_size = untagged_size + 4 bytes; max VLAN IDs = 4094
- L_{untagged}
- original frame size in bytes
Frequently Asked Questions
How do I create and check VLAN interfaces on Linux?
`ip link add link eth0 name eth0.100 type vlan id 100` creates a VLAN subinterface for VLAN ID 100 on eth0; `ip -d link show eth0.100` confirms the VLAN ID and parent link. The `8021q` kernel module must be loaded (`modprobe 8021q`).
Why is the maximum VLAN ID 4094 and not 4096?
The 12-bit VLAN ID field spans 0-4095, but VLAN ID 0 is reserved to mean 'no VLAN, priority tag only' and VLAN ID 4095 is reserved by the 802.1Q standard for implementation use — leaving 1-4094 as the usable range for actual VLAN identifiers.
Does VLAN tagging overhead ever cause frames to exceed the MTU?
Yes — adding the 4-byte tag to an already-maximum-size 1500-byte payload frame can push it to 1504 bytes, which is why 802.1Q-aware switches and NICs typically support 'baby giant' frames (1500 + a few bytes) to accommodate tagged traffic without fragmentation.