A bastion, also known as a bastion host, is a specially secured server that acts as the single, controlled entry point into a private network. Instead of exposing internal systems directly to the internet, administrators connect to the bastion first and then access internal resources from there. This design greatly improves security and visibility.
What Problem a Bastion Solves
In many environments, servers, databases, and services should never be directly accessible from the internet. However, administrators still need a way to manage them.
Without a bastion:
- Multiple servers may be exposed to the public internet
- Each system needs its own security rules
- Tracking and auditing access becomes difficult
A bastion solves this by concentrating access through one tightly locked and monitored system.
How a Bastion Works
A bastion is typically placed in a public facing network segment, such as a DMZ or public subnet. It has very limited functionality and is hardened to reduce risk.
The usual access flow looks like this:
- An administrator connects to the bastion using SSH or RDP
- Authentication and authorization are verified
- Access is logged and monitored
- The administrator connects from the bastion to internal systems
Internal servers accept connections only from the bastion, not from the internet.
Key Security Characteristics
Hardened Configuration
Bastions run minimal software to reduce vulnerabilities. Unnecessary services are disabled, and operating system updates are tightly managed.
Strong Access Controls
Access is restricted using:
- IP allowlists
- Key based authentication
- Multi factor authentication
- Role based access
Centralized Logging
Every connection goes through the bastion, making it easier to:
- Audit who accessed what and when
- Detect suspicious behavior
- Meet compliance requirements
Common Use Cases
1. Cloud Infrastructure Management
Bastions are widely used in cloud environments to manage virtual machines that live in private networks.
2. Database and Backend Access
Databases often sit in private subnets and are accessed only through a bastion to prevent exposure.
3. Production System Operations
Sensitive production systems can be managed securely without opening inbound internet access.
Bastion vs Direct Access
Direct access exposes each system individually and increases attack surface.
A bastion limits exposure to one controlled gateway, reducing risk and improving oversight.
Best Practices
- Use one bastion per environment or region
- Apply strict firewall rules and network segmentation
- Enable session logging or recording
- Rotate credentials regularly
- Monitor and alert on unusual access patterns
Frequently Asked Questions
What is Bastion?
A bastion, also known as a bastion host, is a specially secured server that acts as the single, controlled entry point into a private network. Instead of exposing internal systems directly to the internet, administrators connect to the bastion first and then access internal resources from there.
How does Bastion work?
Bastion works by combining the components described in the sections above. The main page walks through the architecture, the typical use cases, and the trade-offs to weigh before adopting it.
Why does Bastion matter?
Teams adopt Bastion to ship faster, run more reliably, and reduce the cognitive load on engineers. The benefits, limits, and adjacent tools are covered in the body above.
When should you use Bastion?
Use Bastion when the problems it solves match what your team is hitting today. The page above outlines the signals that mean you should adopt it now, and the cases where a simpler approach is fine.
