Security Lists and Route Tables are both essential components of Oracle Cloud Infrastructure (OCI) networking, but they serve different purposes:
Lets consider we have a Virtual Cloud Network (VCN) in Oracle Cloud Infrastructure (OCI) with two subnets:
- Subnet A: Public subnet hosting web servers accessible from the internet.
- Subnet B: Private subnet hosting database servers that should not be directly accessible from the internet and only from subnet A
- Security Lists:
- Function: Security lists act as virtual firewalls for the subnets within your Virtual Cloud Network (VCN).
- Purpose: They control the traffic entering and exiting the subnets by defining sets of ingress and egress rules.
- Scope: Security lists are applied at the subnet level, meaning they affect all the instances within the subnet.
- Rules: Each security list contains rules that permit or deny traffic based on the source and destination IP addresses, protocols, and ports.
- Security List Example:
| Subnet | Direction | Protocol | Port(s) | Source | Destination | Description |
|---|---|---|---|---|---|---|
| Subnet A | Ingress | TCP | 80, 443 | 0.0.0.0/0 (any) | Subnet A | Allow HTTP/HTTPS from anywhere |
| Subnet A | Egress | Any | Any | Subnet A | 0.0.0.0/0 | Allow all outbound traffic |
| Subnet B | Ingress | TCP | 1521 | Subnet A | Subnet B | Allow Oracle Database from Subnet A |
| Subnet B | Egress | Any | Any | Subnet B | 0.0.0.0/0 | Allow all outbound traffic |
- Route Tables:
- Function: Route tables determine where network traffic is directed within the VCN.
- Purpose: They contain a set of rules (routes) that specify how traffic should be routed between different destinations.
- Scope: Route tables are applied at the subnet level, similarly to security lists.
- Routing: Routes within a route table define the next hop for traffic destined to specific IP ranges. This can include destinations within the VCN, internet, on-premises networks (via Dynamic Routing Gateways), or other services in OCI.
- Default Route: Route tables typically include a default route that directs traffic to an Internet Gateway for internet-bound traffic or a NAT Gateway for private subnet traffic destined for the internet.
- Route Table Example
| Subnet | Destination | Target | Description |
|---|---|---|---|
| Subnet A | 0.0.0.0/0 | Internet Gateway | Route all traffic to the internet gateway |
| Subnet A | VCN CIDR | Local | Route traffic within the VCN locally |
| Subnet B | 0.0.0.0/0 | Internet Gateway | Route all traffic to the internet gateway |
| Subnet B | VCN CIDR | Local | Route traffic within the VCN locally |