VxLAN for Networking AI Era
Scale-out multi-tenant overlays, high-radix Clos topologies, and lossless RoCEv2 transport for ultra-large distributed AI training fabrics.
Why VXLAN in Modern Architectures?
Overcoming Layer-2 limits with Layer-3 ECMP scale and dynamic BGP EVPN control planes.
16M Layer 2 Overlays
Breaks the 4,096 VLAN limitation by introducing a 24-bit VXLAN Network Identifier (VNI), enabling massive multi-tenancy in hyper-scale cloud & AI fabrics.
L3 ECMP Underlay
Runs transparently on routed IP networks using all available Equal-Cost Multi-Path (ECMP) links without spanning tree protocol (STP) blocked ports.
AI & GPU Cluster Ready
Seamlessly isolates AI tenants and distributes AllReduce / collective communication across multi-node GPU systems with RoCEv2 encapsulation.
VXLAN in the Era of AI & GPU Training
How modern AI data centers leverage EVPN-VXLAN with RDMA and RoCEv2 for high-throughput tensor parallelism.
1. RoCEv2 & RDMA Encapsulation
RDMA over Converged Ethernet v2 (RoCEv2) packets encapsulated within VXLAN tunnels allow seamless L2 adjacency across leaf-spine pods while maintaining sub-microsecond latency.
2. Flow Entropy & ECMP Hashing
The VXLAN outer UDP source port is calculated from an inner header hash (e.g. 5-tuple flow). This provides high entropy for spine switches to distribute AI elephant flows across all spine links.
3. BGP EVPN Control Plane
Eliminates flood-and-learn multicast reliance by using MP-BGP EVPN (RFC 8365) for host MAC/IP route advertisement and ARP suppression across GPU compute nodes.
4. Buffer Management & Congestion
Outer DSCP copying guarantees that Priority-based Flow Control (PFC) and Explicit Congestion Notification (ECN) marking remain intact across the underlay.
VXLAN Encapsulation Anatomy
Click on any header segment below to inspect byte boundaries, fields, and RFC requirements.
VXLAN Header (8 Bytes)
The VXLAN header contains flags, reserved fields, and the 24-bit VXLAN Network Identifier (VNI).
| Bit Range | Field | Description |
|---|---|---|
| Bits 0-7 | Flags (0x08) | Bit 3 is I-flag (VNI valid). Remaining bits reserved and must be 0. |
| Bits 8-31 | Reserved (24 bits) | Must be set to 0 on transmit, ignored on receipt. |
| Bits 32-55 | VNI (24 bits) | VXLAN Network Identifier designating the virtual overlay segment. |
| Bits 56-63 | Reserved (8 bits) | Must be set to 0 on transmit. |
Interactive MTU & Overhead Calculator
Calculate exact frame overhead and required underlay MTU for your cloud or AI fabric.
Quick Specification Reference
Key parameters for network engineers and system administrators.
Core VXLAN Parameters
- Standard: IETF RFC 7348
- IANA Port: UDP 4789
- Linux Kernel Default: UDP 8472
- Identifier Size: 24-bit VNI (16,777,216 IDs)
- Default Encapsulation: MAC-in-UDP
Ubuntu Linux Kernel Commands
# Add VXLAN interface in Ubuntu / Linux
ip link add name vxlan100 type vxlan \
id 100 \
dstport 4789 \
local 192.168.10.1 \
dev eth0
# Bring up interface
ip link set up dev vxlan100
ip addr add 10.0.100.1/24 dev vxlan100