Cloud Networking

Hybrid Cloud Connectivity

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LearnStep 1 of 3

Architecting Hybrid Connectivity

Learning Objectives

•Evaluate trade-offs between Site-to-Site VPN and dedicated connections like Direct Connect/ExpressRoute.
•Architect secure hybrid network topologies using Transit Gateways and Customer Gateways.
•Implement hybrid DNS resolution strategies to resolve names across on-premises and cloud environments.
•Analyze bandwidth and latency requirements to select the appropriate connectivity model for distributed systems.

Lesson Outline

LearnStep 1/3

Architecting Hybrid Connectivity

Bridging On-Premises and Cloud

For senior engineers, hybrid cloud isn't just about connectivity; it's about extending the data center's control plane while leveraging the cloud's elasticity. The two primary mechanisms for this are Site-to-Site (S2S) VPNs and Dedicated Network Connections (AWS Direct Connect, Azure ExpressRoute, GCP Cloud Interconnect).

1. Site-to-Site VPN (IPsec)

S2S VPNs utilize the public internet to create encrypted tunnels between your Customer Gateway (CGW) and a Virtual Private Gateway (VGW) or Transit Gateway. They are cost-effective and quick to provision but suffer from internet jitter and variable latency.

Key Configuration Parameters:

IKE Version: IKEv2 is preferred for better security and performance (NAT-T support).
Routing: Dynamic routing via BGP (Border Gateway Protocol) is essential for failover and scalability compared to static routing.
Redundancy: Always configure dual tunnels. AWS, for example, provides two endpoints per VPN connection for high availability.

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2. Dedicated Connections (Direct Connect / ExpressRoute)

These bypass the public internet, offering consistent latency, higher bandwidth (up to 100 Gbps), and reduced egress fees. They require physical cross-connects at colocation facilities.

Private VIF (Virtual Interface): Connects to private VPC resources.
Public VIF: Connects to public cloud services (S3, DynamoDB) without traversing the internet.
Transit VIF: Connects to a Transit Gateway for multi-VPC topologies.

3. Hybrid DNS Resolution

Resolving cloud hostnames from on-prem and vice versa requires a forwarding strategy. Cloud-native resolvers (like Route 53 Resolver Inbound/Outbound endpoints) act as bridges.

Inbound Endpoint: Allows on-prem servers to query cloud private hosted zones.
Outbound Endpoint: Forwards queries for on-prem domains (e.g., corp.internal) to on-prem DNS servers.

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4. Bandwidth & Latency Considerations

TCP throughput is inversely proportional to RTT and packet loss (Mathis Equation). For high-throughput hybrid data transfers, even minor latency spikes on a VPN can degrade performance significantly. Jumbo frames (MTU 9001) are often supported on Direct Connect but fragmented on VPNs (MTU 1500 or lower due to IPsec overhead).