
High Performance Encryption (HPE) is an Aviatrix technology that enables 10 Gbps and higher IPsec performance between two single Aviatrix Gateway instances or between a single Aviatrix Gateway instance and on-prem Aviatrix appliance.
You can change Gateway Size if needed to change gateway throughput. The gateway will restart with a different instance size.
IP addresses per network interface
The following tables list the maximum number of network interfaces per instance type, and the maximum number of private IPv4 addresses and IPv6 addresses per network interface:

Constraints
- Although increasing the size of an Amazon EC2 instance for a gateway can be considered an online operation (since traffic can be diverted to other spokes), it still requires a re-attachment process to bring the additional tunnels up. In other words, even though the traffic can be directed to other spokes during the instance size upgrade, the process still requires a re-attachment step to enable the new tunnels and ensure that the gateway functions properly with the increased capacity.
- When decreasing the size of an Amazon EC2 instance that requires removing IP addresses from the network interface, it’s not possible to do so online. This means that the instance must be stopped and the network interface detached in order to remove the IP addresses that are no longer available for the new instance type. In the specific example provided, reducing the instance size from a c5n.18xlarge to a c5n.9xlarge would require removing 20 IP addresses, which cannot be done without detaching the network interface from the instance.

Initial Scenario
- gateways are c5n.large:

- number of secondary IPs:

- number of tunnels:

Scale Up
I’m going to scale to a c5n.9xlarge:

- 1x Private IP and 29 Secondary IPs:

- Number of tunnels:

Tunnels are created or destroyed only during an de/attachment operation.
- 14 tunnels per transit gateway after detaching and attaching:
The number of tunnels depends on the transit gateway size.

Scale Down
From c5n.9xlarge to c5n.4xlarge:

Decreasing to smaller sizes
- c5n.2xlarge:


- c5n.large:

References
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/MultipleIP.html
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html