OpenStack Networking Essentials by Denton James

Author:Denton, James [Denton, James]
Language: eng
Format: azw3, epub
Publisher: Packt Publishing
Published: 2016-04-19T04:00:00+00:00

VXLAN networks

Virtual eXtensible Local Area Network (VXLAN), is an overlay network technology that helps address scalability issues seen with VLANs. Where the maximum number of VLAN networks is 4,096 for a single switching layer, up to 16 million VXLAN networks can exist per VXLAN Tunnel End Point (VTEP). VXLAN encapsulates Layer 2 Ethernet frames inside Layer 4 UDP packets that can be forwarded or routed between hosts. This means that a virtual network can be transparently extended across a large network, such as the Internet, without any changes to the end hosts. However, in the case of Neutron, a VXLAN mesh network is commonly constructed only between infrastructure nodes that exist in the same general location.

Rather than using VLAN IDs to differentiate networks, VXLAN uses a VXLAN Network Identifier (VNI) to function as the unique network identifier on a link that potentially carries traffic for tens of thousands, or millions, of different networks. With Neutron, virtual machine instances are unaware that VXLAN is used to connect traffic between hosts. The VTEP on the physical node handles the encapsulation and decapsulation of traffic without the instance ever knowing.

On a host using the LinuxBridge driver, when a Neutron VXLAN network is created, an interface is created on each host and is responsible for encapsulating and decapsulating traffic for that particular network:

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