Basic Concepts¶
EIP¶
EIP is a static, public IP address.
An EIP can be directly accessed over the Internet. A private IP address is an IP address on a local area network (LAN) and cannot be routed through the Internet.
You can bind an EIP to an ECS in your subnet so that the ECS will be able to communicate with the Internet through a fixed public IP address.
Each EIP can be used by only one ECS at a time. If you want multiple ECSs in the same VPC to share an EIP, you have to use a NAT gateway. For more information, see the NAT Gateway User Guide.
SNAT Connections¶
An SNAT connection consists of the source IP address, source port, destination IP address, destination port, and a transport layer protocol. The source IP address is the EIP, and the source port is the EIP port. An SNAT connection uniquely identifies a session.
DNAT Connections¶
A DNAT connection enables servers in a VPC to share an EIP to provide services accessible from the Internet.