Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about the principle of L2 Population. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Today we are talking about L2 Population, which is closely related to VXLAN.

L2 Population is used to improve the Scalability of VXLAN networks.

Usually we say that the Scalability of a system is good, which means that when the scale of the system becomes larger, it can still work efficiently.

What kind of Scalability problem does L2 Population solve?

Please take a look at the following picture:

This is a VXLAN network with five nodes, with several VM running on each node.

Now suppose VM An on Host 1 wants to communicate with VM G on Host 4.

The first step for VM An is to learn the MAC address of VM G.

So VM A needs to broadcast APR messages throughout the VXLAN network: "what is the MAC address of VM G?"

If the VXLAN network has a large number of nodes, the cost of broadcasting will be high, so Scalability will become a problem.

Luckily, L2 Population showed up.

The function of L2 Population is to provide Porxy ARP function on VTEP, so that VTEP can know the following information in VXLAN network in advance:

1. VM IP-MAC correspondence

2. The correspondence between VM and VTEP

When VM A needs to communicate with VM G:

1. The VTEP on Host 1 directly responds to the APR request of VM A, telling the MAC address of VM G.

two。 Because VTEP on Host 1 knows that VM G is located in Host 4, it sends the encapsulated VXLAN packet directly to the VTEP of Host 4.

In this way, the problems of MAC address learning and APR broadcasting are solved, and the Scalability of VXLAN is guaranteed.

So the next key question is:

How did VTEP get the information about IP-MAC-VTEP in advance?

The answer is:

Neutron knows the status and information of each port; port holds IP,MAC-related data.

When instance starts, its port state changes as follows: down-> build-> active.

Whenever the state of the port changes, the Neutron notifies the Neutron agent on each node through the RPC message, so that the VTEP can update the relevant information of VM and port.

Based on this information, VTEP can determine which VM are on other Host, as well as their MAC address, so that it can communicate with them directly, thus avoiding unnecessary tunnel connections and broadcasts.

After understanding how it works, we'll learn how to configure L2 Population in Neutorn in the next section.

This is what the L2 Population principle shared by the editor is. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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