AWS SAA: Networking & Load Balancing Study Guide

Flashcards covering key vocabulary and concepts related to AWS Networking and Load Balancing as outlined in the SAA-C03 study guide.

Network Load Balancer (NLB)

Primary Use Case: Extreme performance (millions of requests per second), ultra-low latency, or Static IP requirements.

Gateway Load Balancer (GWLB)

Primary Use Case: Deploying and managing third-party virtual appliances (Firewalls, IDS/IPS) inline with network traffic.

OSI Layer 4 (Transport) Focus

TCP/UDP Protocols and Ports. It does not inspect the content of the message.

OSI Layer 7 (Application) Focus

HTTP/HTTPS Content. It inspects headers, paths, cookies, and payloads.

Which Load Balancer natively preserves Client IP?

Network Load Balancer (NLB).

How to see Client IP behind an ALB

Inspect the 'X-Forwarded-For' HTTP header.

Required Load Balancer for AWS WAF

Application Load Balancer (ALB). WAF cannot attach to an NLB directly.

TCP Passthrough

Sending encrypted traffic (HTTPS) through a Layer 4 Load Balancer without decrypting it.

Path-Based Routing Layer

Layer 7 (Application). Requires an ALB to read the URL path (e.g., /images).

Protocol used by Gateway Load Balancer

GENEVE (Generic Network Virtualization Encapsulation) on port 6081.

Does Port 443 always mean Layer 7?

No. An NLB can forward Port 443 traffic at Layer 4 without acting as a Layer 7 proxy.

Sticky Sessions (Session Affinity)

A mechanism to route requests from the same client to the same target (EC2) for a duration.

Cross-Zone Load Balancing

Distributes traffic evenly across all registered targets in all enabled Availability Zones.

Load Balancer for Static IP requirement

Network Load Balancer (NLB). ALBs do not have static IPs.

Connection Draining (Deregistration Delay)

Allows a target to complete in-flight requests before being removed from service.

Target Group

Logical grouping of targets (EC2, IP, Lambda) that a Load Balancer routes traffic to.

504 Gateway Timeout on ALB

The application (target) failed to respond within the configured timeout period.

503 Service Unavailable on ALB

Usually indicates no registered targets are healthy in the Target Group.

SNI (Server Name Indication)

Allows a load balancer to host multiple TLS certificates for different domains on the same listener.

ALB Routing Criteria

Host header, Path, HTTP header, HTTP method, Query string, Source IP.

NLB Routing Criteria

IP Protocol, Source IP, Destination Port, TCP Sequence Number.

Can NLB handle UDP traffic?

Yes. NLB is the only ELB that supports UDP.

Health Check Layer for NLB

Can be TCP (Layer 4 connectivity) or HTTP/HTTPS (Layer 7 response).

Only Load Balancer to support Lambda targets

Application Load Balancer (ALB).

Key difference: Route 53 vs. Load Balancer

Route 53 is DNS (Phone book). Load Balancer is Traffic Distribution (Switchboard).