You can select different specifications for NAT Gateway to adjust the performance metrics (maximum connections and the number of new connections per second). However, data throughput is not affected.

The following table lists the available specifications for NAT Gateway.
Specification Maximum number of SNAT connections Number of new SNAT connections established per second
Small 10,000 1,000
Medium 50,000 5,000
Large 200,000 10,000
Super Large-1 1,000,000 30,000
Note the following when selecting a specification:
  • NAT Gateway specifications impact SNAT performance only (they do not affect DNAT performance).

  • There is no correlation between a specification and the number of IPs.

  • CloudMonitor only provides monitoring data on the maximum number of connections. It does not provide monitoring data on CPS.

  • The timeout period of an SNAT connection is 900 seconds.

  • To avoid SNAT connection timeout caused by network congestion and public network jitter, make sure that your service application has implemented automatic reconnection to provide higher availability.

  • Currently, NAT Gateway does not support packet fragmentation.

  • For the same destination public IP address and port, the number of EIPs that are associated with a NAT Gateway affects the maximum number of connections that the NAT Gateway can handle. If the NAT Gateway is associated with only one EIP, the maximum number of connections is 50,000. If multiple EIPs are associated, this number is 50,000 multiplied by the number of EIPs..
  • ECS instances in a VPC that are not associated with any public IP addresses can access the Internet through a NAT Gateway. If the bandwidth at which the ECS instances access the same public IP address and port is greater than 2 Gbit/s, packets may be discarded due to limited ports. To resolve this issue, we recommend that you associate four to eight EIPs with the NAT Gateway and create a SNAT pool.