Day 07 - VPC Routing & Network Interfaces

Date: 2025-09-16 (Tuesday)
Status: “Done”

Lecture Notes

VPC Routing & ENI

Route Tables

  • A route table defines how traffic is directed.
  • Each VPC has a default route table containing only a local route allowing internal communication between subnets.
  • Custom route tables can be created, but the local route cannot be deleted.

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Elastic Network Interface (ENI)

  • An ENI is a virtual network card that can be moved between EC2 instances.
  • It retains its private IP, Elastic IP address, and MAC address when reassigned.
  • Elastic IP (EIP) is a static public IPv4 address that can be associated with an ENI.
  • Unused EIPs incur charges.

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ENI Use Cases:

  • Management network separate from data network
  • Network and security appliances
  • Dual-homed instances with workloads on distinct subnets
  • Low-budget, high-availability solution

VPC Endpoints

  • A VPC Endpoint enables private connectivity to supported AWS services via AWS PrivateLink without using the public Internet.
  • Two types:
    • Interface Endpoint: Uses an ENI with a private IP.
    • Gateway Endpoint: Uses route tables (available for S3 and DynamoDB only).

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Hands-On Labs

Lab 03 – Amazon VPC & Networking (continued)

  1. Create Internet Gateway (IGW) → 03-03.3
  2. Create Route Table (Outbound via IGW) → 03-03.4
  3. Create Security Groups → 03-03.5