VXLAN
VXLAN (Virtual Extensible Local Area Network):
It is a replacement of VLAN
VLAN ID is 12 bits i.e. 4096, VXLAN ID is 24 bits i.e. 16.78 million
It is helpful in multi-tenancy
It is an overlay tunnel, ethernet over IP tunnel (L2 over L3) (mac over IP)
VXLAN is UDP tunnel
L3 can be IGP (OSPF, EIGRP, ISIS) or point-to-point
Standard (RFC 7348, RFC 7432) based, means not specific to any vendor
It has scaling enhancement, better control plane management
ECMP (Equal Cost Multi Pathing) means no STP works in CLOS Fabric (Spine & Leaf)
VXLAN Terminology:
Underlay like Internet
IGP
PIM – multicast reachability
BGP – Establishing VXLAN control plane
Overlay will be like s2s vpn tunnel
Bridging – with in the segment
Routing – multiple segments
VNI/VNID – VXLAN number
VTEP (VXLAN Tunnel Endpoint): The peer device which does the encapsulation and decapsulation
Leaf switches will VTEP in CLOS Fabric
VXLAN Segment
VXLAN Gateway: The device which forwards the traffic between the VXLANs
NVE (Network Virtualization Edge) – logical representation of VTEP
VXLAN Headers:
Headers: Ethernet — IP — UDP — VXLAN – Frame…. Encapsulated
Frame contains Source mac, Destination mac, source IP, Destination IP
VXLAN contains VNI
8bit (reserved for future use, all 0’s) — 24 bit (VNI) — 8bit (reserved for future use, all 0’s) — Flag (8 bits, 00100000, 1 means VNI is valid)
UDP contains Source port (random), Destination port (4789)
IP contains Source IP, Destination IP of other end device
Ethernet contains Source mac, Destination mac of other end device
Jumbo frame has to be set as there is a lot of encapsulation overload (more than 50 bytes)
If we don’t set higher MTU, VXLAN will not function properly, because fragmentation will delay the exchange of data