Elastic IP

What is Elastic IP?

An elastic IP address (EIP) functions based on the NAT technology. IP addresses in a private network are translated into an EIP that is in another network. This way, private networks can be accessed from other networks by using EIPs.

Concepts

Public EIP: The EIP service provided by a virtual IP address (VIP) created from a public network.
- The private network is an isolated network that cannot be directly accessed from other networks or the Internet. A public EIP can directly associate the access to a public network with the VM IP of the private network.
- A public EIP can be associated with or disassociated from a VM instance dynamically.
- A public EIP can be associated with VM instances created from private networks, such as flat networks and VPC networks.
  - The public EIP realized by a distributed EIP can access flat networks through public networks.
  - A VPC vRouter can be used to access VPC networks through public networks.
Flat EIP: The EIP service provided by a VIP created from a flat network.
- L3 isolations exist between flat networks of different network ranges. Therefore, these flat networks cannot be accessed directly. A flat EIP can be used to associate the access to one flat network with the VM IP created from another flat network.
- A flat EIP can be associated with or disassociated from a VM instance dynamically.
- A flat EIP can be associated with VM instances created from other flat networks.

Scenarios

EIP usage in a flat network scenario:
The following diagram shows how an EIP is used in a flat network scenario.

Figure 1. EIP Usage in Flat Network Scenario
- Public networks can connect to the Internet through firewalls.
- Flat networks provide IP addresses for VM instances in each compute node. Notice that these IP addresses cannot connect to the Internet by default.
- A distributed EIP is deployed on each compute node, and can be associated with public networks or private networks separately.
EIP usage in a VPC network scenario:
The following diagram shows how an EIP is used in a VPC network scenario.

Figure 2. EIP Usage in VPC Network Scenario

Considerations

When you use an EIP, note that:

An instance can have only one EIP associated at a time.
The EIP association and disassociation operations take effect in real time.
Associating or disassociating an EIP does not affect the running of an instance.

Create an Elastic IP

On the main menu of ZStack Cloud, choose Resource Center > Network Service > Basic Network Service > EIP. On the EIP page, click Create EIP. Then, the Create EIP page is displayed.

On the displayed page, set the following parameters:

Name: Enter a name for the EIP.
Description: Optional. Enter a description for the EIP.
You can use a virtual IP address by using either of the following methods:
- VIP: Select Create VIP.
  - Network: Select an L3 network to create a VIP. The network can be a public network or a flat network.
    Note: Currently, you cannot create a VIP with a flat network disabled with IP address management.
  - Network Range: Optional. Select a network range.
    Note:
    - If you selected an IPv4 public network, you can select a normal network range or an address pool. If you selected an IPv6 public network, you can only select a normal network range.
    - If you selected an IPv4 or IPv6 public network, you can only select a normal network range.
    - If you selected an IPv4 VPC network, you can only select a normal network range.
  - Assign IP: Optional. You can assign a virtual IP address.
    Note:
    - If left blank, the system automatically assigns a VIP.
    - If you do not select a network range, you can specify an IP address only from a normal network range.
- VIP: Select Use Existing VIP.
  Set the following parameter:
  - VIP: Select an existing VIP.
Figure 1. Create EIP

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