Route Table
Definition
A set of rules (called routes) that determine where network traffic from subnets or gateways is directed, optimizing data flow and routing.
Use Cases
- Netflix: Segmenting public and private application tiers in AWS so only the public tier is directly reachable from the internet. — In AWS VPCs, public subnets use a route table with 0.0.0.0/0 pointing to an Internet Gateway, while private subnets use a different route table with 0.0.0.0/0 pointing to a NAT Gateway for outbound-only access. Security groups and NACLs further restrict inbound traffic. (Reduced attack surface by keeping backend services off the public internet while still allowing controlled outbound access for updates and dependencies.)
- Spotify: Controlling egress paths for private workloads in Google Cloud to keep traffic on private connectivity where possible. — Uses Google Cloud VPC routes to direct traffic to specific next hops (such as Cloud VPN/Cloud Interconnect paths via dynamic routing with Cloud Router, and default routes for internet egress) and applies routing priorities to prefer private paths over broader routes when both match. (Improved network control and predictability for service-to-service communication and reduced reliance on public internet paths for internal connectivity.)
- Adobe: Hub-and-spoke networking in Azure to centralize security and shared services. — Associates Azure Route Tables (UDR) to spoke subnets to steer traffic to a central hub (often via a virtual network gateway or a network virtual appliance) for inspection and shared services, while keeping system routes for local VNet traffic. (Centralized governance and consistent traffic inspection across many application networks.)
Provider Equivalents
- AWS: Amazon VPC Route Tables
- Azure: Azure Route Tables (User Defined Routes, UDR)
- GCP: Google Cloud VPC routes
- OCI: OCI VCN Route Tables
Frequently Asked Questions
- What's the difference between a Route Table and a security group (or firewall)?
- A route table decides where traffic goes (the next hop) based on destination IP ranges. A security group/firewall decides whether traffic is allowed or denied. Routing is about path selection; security rules are about permission.
- When should I use a Route Table?
- Use route tables whenever you need to control traffic paths, such as: making a subnet public (send 0.0.0.0/0 to an Internet Gateway), keeping a subnet private (send 0.0.0.0/0 to a NAT device), forcing traffic through a firewall/NVA, connecting to on-prem networks via VPN/Direct Connect/Interconnect, or steering traffic to peered networks and service endpoints.
- How much does a Route Table cost?
- Route tables/routes are typically not billed as a standalone item in major clouds, but the targets they point to can cost money. Common cost drivers include NAT Gateways/NAT instances, VPN gateways, interconnect/direct connect circuits, network virtual appliances, and data transfer/egress charges. Always check the pricing for the specific next-hop service and for data processing/egress in your region.
Category: networking
Difficulty: intermediate
Related Terms
See Also