Introduction
While studying for CompTIA Network+, I couldn't grasp what VNI is.
I could only memorize that " VNI is the number used to identify a VXLAN network", but I couldn't totally understand what it is and what it differ from VLAN.
Once I matched familiar example with it, everything fell into place, so I decided to write it down.
The difference between VLAN and VXLAN
First of all, we need to understand the difference between them to comprehend VNI.
What is VLAN
VLAN = Virtual LAN
A mechanism for dividing physical network into virtual segments within the same switch or building.
┌────────────────────────────┐
│ A switch │
│ VLAN10 │ VLAN20 │ VLAN30 │
└────────────────────────────┘
Physical constraint：
→ The same switch or until the adjacent switch
→ It cannot reach long distance
→ Max : 4094
VLAN limitation
In a cloud environment, it is essential to divide network for each tenant ( enterprise )
Thousand or ten thousand networks are needed
↓
VLAN's maximum of 4094 is far from sufficient for this scale
What is VXLAN
VXLAN = Virtual Extensible LAN
A mechanism that extends VLAN to create networks beyond physical boundaries.
Datacenter A Datacenter B
┌─────────┐ ┌─────────┐
│ Server │─── VXLAN ───│ Server │
└─────────┘ Tunnel └─────────┘
VLAN：
→ No tunnel
→ Segments are divided using physical switch ports
VXLAN：
→ UDP Tunnel（ Port 4789）
→ Layer 2 Frame is transferred on Layer 3 network
→ It can overcome the physical constraint
Compare VLAN with VXLAN
| Category | VLAN | VXLAN |
|---|---|---|
| Purpose | Divide physical NW | Create NW beyond place |
| Identifier | VLAN ID（12bit） | VNI（24bit） |
| Maximum | 4094 | 16million |
| Range | Inside building | Regardless of the place |
| Transfer | Layer 2 | UDP（ On Layer 3） |
| Use | Small or medium-scale environment | Large-scale cloud environment |
Understanding with familiar example
VLAN：
→ Segment rooms for each floor inside a building
→ It can just us inside the area
VXLAN：
→ It can use every office (Tokyo, Osaka, Fukuoka) virtually as the same floor
→ It can surpass physical distance
What is VNI
VXLAN Network Identifier
In a nutshell, ** it is the number used to identify a virtual network created by VXLAN **.
VLAN ID = VLAN identification number（12bit・max 4094）
VNI = VXLAN identification number（24bit・max 16million）
VNI is an extended version of VLAN ID
→ VLAN ID is 12bit
→ VNI is 24bit
→ This allows approximately 4000 times more identifiers
Understanding with postcode
VLAN ID：
→ Apartment room number （Max 4094 rooms）
→ Lack for large-scale environment
VNI：
→ Country's postcode（ Max 16 million）
→ It can accommodate any scale of environment
The mechanism of VXLAN
VXLAN uses a UDP tunnel to transfer Layer 2 frames over Layer 3 network
┌───────────────────────────────────────────────────────────────┐
│ VXLAN Packet │ │ │
│ ┌─────────────────────────────┐ │ │ │ │ │
│ │ Original Layer 2 frames │ │ │ │ │ │
│ └─────────────────────────────┘ │
│ VNI（ Identifier that specifies │
│ which virtual network the packet belongs to） │
└───────────────────────────────────────────────────────────────┘
↓
Transfer on UDP port 4789
Summary
VLAN ：
The mechanism to divide network inside building
→ Max 4094・12bit
VXLAN ：
The mechanism to create virtual network beyond building
→ Max 16million・UDP tunnel
VNI ：
An identifying number used to distinguish virtual networks created by VXLAN
→ 24bit・Max 16 million
→ Extended version of VLAN ID
The difference between VLAN and VXLAN：
VLAN → Inside the same building・ Max 4094
VXLAN → Regardless of the building・ Max 16 million
Conclusion
I used to struggle with memorizing that VNI is the identification number for VXLAN.
Once I understood the structure behind each term, I could naturally grasp why VNI is essential.
Top comments (0)