Geneve Overhead Calculator
Work out Geneve encapsulation bytes, the resulting inner MTU and the goodput lost to option TLVs.
About Geneve Overhead Calculator
Geneve is VXLAN's extensible cousin: the same 50-byte IPv4 floor, plus a variable options block that pushes real deployments to 66–74 bytes. Every option byte is taken straight out of the inner MTU, and goodput is the ratio of payload to total frame. Geneve is the encapsulation behind NSX and many cloud overlays, and an inner MTU set from the 50-byte VXLAN figure silently black-holes large flows once options are switched on.
Formula
Geneve Overhead
Geneve overhead = 14 (Ethernet) + 20 or 40 (outer IP) + 8 (UDP) + 8 (Geneve base) + option TLVs; inner MTU = path MTU − overhead.
- Geneve base
- Fixed 8-byte Geneve header carrying the 24-bit VNI
- option TLVs
- 0–252 bytes of variable metadata, always a multiple of 4
Worked example
With the default values below, Geneve Overhead Calculator returns Geneve Encapsulation of 66. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Inner payload MTUaccepts 576–9,000 bytes
- 1,500 bytes
- Underlay path MTUaccepts 576–9,216 bytes
- 1,500 bytes
- Geneve option TLV bytesaccepts 0–252 bytes
- 16 bytes
- Outer IP versionone of IPv4 outer header (20 B), IPv6 outer header (40 B)
- IPv4 outer header (20 B)
- Underlay link rateaccepts 1–800 Gbps
- 25 Gbps
Results
- Geneve Encapsulation
- 66 bytes
- Inner (Tunnel) MTU
- 1,434 bytes
- Overhead of the Frame
- 4.21%
- Tenant Goodput
- 23.946 Gbps
- Header Breakdown
- Ethernet 14 + IP 20 + UDP 8 + Geneve 24 bytes
Step by step
- 1Values used
- 2Geneve Overhead
- 3Geneve Encapsulation= 66 bytes
- 4Inner (Tunnel) MTU= 1,434 bytes
- 5Overhead of the Frame= 4.21
- 6Tenant Goodput= 23.946 Gbps
- 7Header Breakdown= Ethernet 14 + IP 20 + UDP 8 + Geneve 24 bytes
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Geneve Overhead calculated?
Geneve overhead = 14 (Ethernet) + 20 or 40 (outer IP) + 8 (UDP) + 8 (Geneve base) + option TLVs; inner MTU = path MTU − overhead. Geneve is VXLAN's extensible cousin: the same 50-byte IPv4 floor, plus a variable options block that pushes real deployments to 66–74 bytes. Every option byte is taken straight out of the inner MTU, and goodput is the ratio of payload to total frame.
Why does Geneve Overhead matter?
Geneve is the encapsulation behind NSX and many cloud overlays, and an inner MTU set from the 50-byte VXLAN figure silently black-holes large flows once options are switched on.
What values do I need to enter?
This calculator takes 5 inputs: Inner payload MTU, Underlay path MTU, Geneve option TLV bytes, Outer IP version, Underlay link rate. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.