Geneve Overhead Calculator
Work out Geneve encapsulation bytes, the resulting inner MTU and the goodput lost to option TLVs.
Inputs
Geneve Encapsulation
66bytes
Inner (Tunnel) MTU
1,434bytes
Overhead of the Frame
4.21%
Tenant Goodput
23.946Gbps
Header Breakdown
Ethernet 14 + IP 20 + UDP 8 + Geneve 24 bytes
Step by step
Values used
Inner payload MTU = 1,500 bytes; Underlay path MTU = 1,500 bytes; Geneve option TLV bytes = 16 bytes; Outer IP version = IPv4 outer header (20 B); Underlay link rate = 25 Gbps
Geneve Overhead
Geneve overhead = 14 (Ethernet) + 20 or 40 (outer IP) + 8 (UDP) + 8 (Geneve base) + option TLVs; inner MTU = path MTU − overhead.
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
How it works
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
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.