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In the past, each Cornell AWS customer that required access to the private Cornell network in AWS received their own Cornell Standard VPC that provided an AWS VPC for their exclusive use. In contrast, the shared Cornell AWS VPC described in this document provides similar network connectivity in a set of AWS subnets shared among multiple Cornell AWS customers.
Benefits of
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Using the Shared VPC
Cornell AWS customers that opt-in to use the shared Shared VPC will experience the following benefits:
- Less VPC management – The CIT Cloud Team manages manages the subnets, network ACLs, and route tables in the shared VPC. Customers manage the Security Groups applied to their EC2 instances and other resources deployed in the shared VPC.
- Cheaper
- Each Cornell Standard VPC contains at least one NAT Gateway, which typically costs about $1/day to run. In contrast, NAT Gateways deployed in the shared VPC are managed and paid for by CIT.
- VPC Flow Logs in the shared VPC are paid for by CIT.
- Increased resiliency
- Customers using the shared VPC have access to subnets in all of the Availability Zones in the us-east-1 AWS Region. In contrast, the Cornell Standard VPC is typically deployed only to two Availability Zones.
- Each private subnet in the shared VPC utilizes a NAT Gateway local to the Availability Zone where the subnet is deployed. In contrast, private subnets in the Cornell Standard VPC typically utilize a single NAT Gateway in a single Availability Zone.
- Availability Zone matching
- Since the Shared VPC offers access to all Availability Zones in us-east-1, customers have the option to deploy resources in specific AZs if they are trying to deploy resources in the same AZs as deployed by partners or vendors.
Caveats of Using the Shared VPC
There are a few caveats to be aware of when deciding whether to opt-in to use the Shared VPC:
- The Network ACLs used by the Shared VPC may be a bit more permissive than ones a Cornell AWS customer might design for a VPC of their own. Since the Shared VPC supports a plethora of use cases and resource deployment architectures, it cannot be customized (i.e., "locked down") for a single customer. Note that customers do manage the Security Groups applied to their EC2 instances and other resources deployed in the shared VPC so they still decide the ultimate connectivity and access to their resources.
- To be continued...
Use Cases
The Shared VPC supports many, many customer use cases. A few of those are:
- Simple deployment of a few resources that require access to the Cornell private network.
- Deployment of three-tier (or more!) application.
Misuse Cases
Misuse cases are situations where the Shared VPC should not be used. Some of those are:
- Cornell private network access in regions other than us-east-1 (N. Virginia)
- Access to a vast amount of private Cornell IP addresses in AWS
- Need to directly manage Network ACLs, route tables, or other VPC configuration
- VPC peering to non-Cornell VPCs
- Deploying Kubernetes or using EKS (Kubernetes consumes vast numbers of IP addresses, which is incompatible with the Shared VPC model.)