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What is VXLAN?

Latest reply: Feb 9, 2022 10:55:08 488 13 7 0 0

Hello, everyone!

This post will share with you the VXLAN.

What is VXLAN?

Virtual eXtensible Local Area Network (VXLAN) is one of the Network Virtualization over Layer 3 (NVO3) technologies defined by the Internet Engineering Task Force (IETF) and is an extension to Virtual Local Area Network (VLAN). VXLAN encapsulates a Layer 2 Ethernet frame into a UDP packet and transmits the packet over a Layer 3 network.

As shown in Figure 1 VXLAN is essentially a tunneling technology. It establishes a logical tunnel on the IP network between the source and destination network devices to encapsulate user-side packets and forward them through the tunnel. Servers are connected to different ports of network devices in the data center VXLAN network, which can be considered as a virtual Layer 2 switch.

vxlan

VXLAN has become the mainstream technology for constructing data center networks because it can meet the requirements of dynamic virtual machine (VM) migration and multi-tenancy in data center networks.

Why Is VXLAN Required?

Why is VXLAN required? This is closely related to the virtualization trend on the server side of the data center. VMs need to be dynamically migrated after server virtualization, requiring an accessible network. As the data center scale increases, the number of tenants increases sharply, requiring isolation of a large number of tenants. VXLAN can meet the two requirements.

1. Dynamic VM Migration Requires an Accessible Network

What is server virtualization?

The physical server efficiency in traditional data centers is too low (10% to 15% on average), wasting a large number of power resources and equipment room resources. To address this issue, server virtualization technology emerges. As shown in Figure 2, the server virtualization technology virtualizes a physical server into multiple logical servers that are called VMs. Each VM can run independently and has its own operating system, applications, MAC address, and IP address. VMs connect to external networks through the virtual switches (vSwitches) on physical servers.

Server Virtualization?

Server virtualization technology can effectively improve server efficiency and reduce energy consumption and O&M costs, so it has been widely used.

What is dynamic VM migration?

Dynamic VM migration is the process of moving VMs from one physical server to another while ensuring continuity of services deployed on the VMs. End users are unaware of the process, so administrators can flexibly allocate server resources or maintain and upgrade the physical servers without affecting normal server use by end-users.

After server virtualization, dynamic VM migration becomes a common practice. To ensure service continuity during the migration of a VM, the VM's IP address and running status (for example, the TCP session status) must remain unchanged. Therefore, VMs can be dynamically migrated only in the same Layer 2 domain.

As shown in Figure 3, the traditional three-layer network architecture limits the dynamic VM migration scope. The migration can occur only in a limited scope and is greatly restricted.

Traditional three-layer network architecture limit

To enable smooth VM migration in a large scope or even across regions, all involved servers must be deployed on a large Layer 2 domain.

How does VXLAN meet network requirements during dynamic VM migration?

It is well known that a Layer 2 switch can implement Layer 2 communication between servers connected to the switch. When a server is migrated from one part of the Layer 2 switch to another port, the IP address of the server can remain unchanged. This meets the requirements for dynamic VM migration. VXLAN was designed to meet these requirements.

As VXLAN is essentially a tunneling technology, when the source and destination ends need to communicate with each other, a virtual tunnel is created on the IP network of the data center to transparently forward user data between the two ends. In such tunnel establishment mode, almost a full mesh topology can meet the growing communication needs in the data center.

VXLAN can construct a fully connected Layer 2 virtual network based on the data center IP network. This ensures that any two points can communicate with each other through a VXLAN tunnel without focusing on the structure and details of the underlying network. For servers, VXLAN virtualizes the entire data center network into a large Layer 2 virtual switch. All servers are connected to this Layer 2 virtual switch. Servers are unaware of how forwarding is performed within the Layer 2 virtual switch.

VXLAN virtualizing

2. Sharply Increasing Tenants in the Data Center Require Isolation

In a traditional VLAN network, in accordance with standards, a maximum of about 4k VLANs are available. After server virtualization, a physical server hosts multiple VMs. Each VM has an independent IP address and MAC address. Public clouds or other large virtualized cloud data centers need to accommodate tens of thousands of tenants or even more. In this case, VLAN cannot meet these requirements.

How does VXLAN meet these requirements? VXLAN adds a 24-bit VXLAN network identifier (VNI) that is similar to a VLAN ID to a VXLAN header. Theoretically, a maximum of 16M VXLAN segments are supported, meeting the requirements for identification and isolation between large networks. The following describes the functions of VNIs.

That's all, thanks!

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Malikumar
HCIE Created Jan 11, 2022 12:10:53

What is VXLAN?-4593619-1
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Al_Sealand
Created Jan 13, 2022 06:23:06

Great content.
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olive.zhao
olive.zhao Created Jan 13, 2022 06:44:15 (0) (0)
Thanks!  
little_fish
Admin Created Jan 13, 2022 07:47:36

VXLAN
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Nabihazahid
Nabihazahid Created Feb 6, 2022 17:41:33 (0) (0)
 
user_4358465
Created Jan 19, 2022 10:57:32

Good introduction on the topic
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MahMush
Moderator Author Created Feb 6, 2022 17:20:49

learning new things is always exciting

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Funstuff
Moderator Author Created Feb 6, 2022 17:30:08

Thanks for sharing
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SaraZahid
Created Feb 6, 2022 17:41:02

Good
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SaraZahid
Created Feb 6, 2022 17:41:08

Thanks
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Nabihazahid
Created Feb 6, 2022 17:41:41

Thanks for sharing
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