VXLAN/EVPN Calculator

Plan VXLAN overlays, VNI allocation, and EVPN configurations.

VNI Allocation

Allocation Scheme

Base VNI / Offset

Number of VNIs needed

Starting VLAN ID

VNI Allocation Plan

VLAN	VNI	Hex	Multicast Group
Click "Generate VNI Plan" to see results

Fabric Parameters

Number of VTEPs (Leaf switches)

Number of Spine switches

Total VNIs in fabric

Average hosts per VTEP

BUM Replication Mode

Fabric Requirements

Total VTEP IP addresses	-
Underlay P2P links	-
P2P IP addresses needed	-
Loopback IPs needed	-
Recommended Loopback subnet	-
Recommended P2P supernet	-
Total MAC entries (est.)	-
EVPN Type-2 routes (est.)	-
Multicast groups needed	-
BGP sessions per leaf	-

EVPN Parameters

BGP AS Number

VTEP Loopback IP

L2 VNI

VLAN ID

L3 VNI (for VRF)

VRF Name

EVPN Configuration Values

Route Distinguisher (RD)	-
L2 Route Target (RT)	-
L3 Route Target (RT)	-
VNI in Hex	-
VXLAN UDP Port	-
EVI (EVPN Instance)	-
MAC-VRF Name	-
IP-VRF Name	-

Sample Configuration Snippets

! Generate EVPN values to see configuration

! Generate EVPN values to see configuration

# Generate EVPN values to see configuration

MTU Requirements

Inner Payload MTU

Original frame size (typically 1500 for standard Ethernet)

Transport Mode

Encapsulation Options

Inner VLAN tag (802.1Q)

Double VLAN (Q-in-Q)

MTU Breakdown

Original Payload	-
Inner Ethernet Header	-
VLAN Tag(s)	-
VXLAN Header	-
UDP Header	-
Outer IP Header	-
Outer Ethernet Header	-
Total VXLAN Frame	-
Required Underlay MTU	-

Recommended Settings

Configure all underlay interfaces with jumbo frames

About VXLAN/EVPN

VXLAN (Virtual Extensible LAN) is a network virtualization technology that encapsulates Layer 2 Ethernet frames within Layer 3 UDP packets. EVPN (Ethernet VPN) provides a control plane for VXLAN, enabling efficient MAC address learning and BUM (Broadcast, Unknown unicast, Multicast) traffic handling.

Key Concepts

VNI (VXLAN Network Identifier)

24-bit identifier (1-16,777,215) that identifies a VXLAN segment. Similar to VLAN ID but with much larger address space.

VTEP (VXLAN Tunnel Endpoint)

The device that encapsulates/decapsulates VXLAN traffic. Typically a leaf switch or hypervisor.

Route Distinguisher (RD)

Makes VPN routes unique in BGP. Format: ASN:VNI or IP:VNI.

Route Target (RT)

Controls route import/export between VRFs. Format: ASN:VNI.

VXLAN Header Overhead

Component	Size (bytes)	Description
Outer Ethernet	14	Destination + Source MAC + EtherType
Outer IP (v4/v6)	20/40	Source + Destination VTEP IPs
UDP	8	Source port (hash) + Dst port 4789
VXLAN	8	Flags + VNI + Reserved
Total Overhead	50/70	IPv4/IPv6 underlay