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Routing & Switching · Intermediate

Virtual Extensible LAN (VXLAN)

An overlay encapsulation (RFC 7348) that carries Layer 2 frames inside UDP/IP packets, identified by a 24-bit VNI.

Definition

VXLAN supports about 16 million segments versus 4094 VLANs and lets Layer 2 domains stretch across a routed Layer 3 underlay. Frames are encapsulated with an 8-byte VXLAN header, UDP (destination port 4789), outer IP and outer Ethernet headers, adding about 50 bytes. VTEPs perform encapsulation; the control plane is flood-and-learn or BGP EVPN.

Example

interface nve1 / member vni 10010 / source-interface loopback1

Exam tip

Remember UDP 4789, 24-bit VNI and roughly 50 bytes of overhead requiring jumbo MTU in the underlay.

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