Bastion Host

How bastion hosts work

The bastion sits right at the boundary: reachable from outside, permitted to reach inside. Administrators connect to it first, SSH to a Linux bastion or RDP to a Windows one, authenticate, then hop onward to internal systems from there. Firewall rules enforce the funnel, since internal servers accept administrative connections only from the bastion's address, which collapses the entire admin attack surface down to one deliberately hardened machine. Hardening means a minimal OS, no extraneous services, aggressive patching, strong authentication, and full session logging. The bastion is deliberately exposed as a controlled administrative entry point and therefore requires especially strong hardening and monitoring.

Bastion host vs jump host

The terms overlap so much that people use them interchangeably, but the distinction is worth keeping. A jump host (jump box) is any intermediary machine used to hop between network zones. The term just describes the role in the path. A bastion host is a jump host that was actually built and operated as a security control: hardened, minimal, monitored, exposed on purpose. Every bastion is a jump host. A casually maintained utility VM someone uses for hopping is a jump host that would fail the bastion standard badly.

Administrative RDP and SSH access

Bastions exist mostly for administrators. The SSH pattern uses agent forwarding or ProxyJump through a Linux bastion to reach fleet servers. The Windows pattern RDPs to a bastion, then RDPs onward to internal hosts from there. Both patterns concentrate privileged credentials on that one bastion, which is exactly why credential hygiene there matters so much. No cached domain admin sessions, MFA at the bastion, just-in-time elevation: get these wrong and the design hurts more than it helps.

Security benefits, and concentrated risk

The benefit is just arithmetic: one exposed, hardened system instead of dozens of exposed servers, one place to enforce MFA and record sessions, one choke point for policy. The risk is that same arithmetic run backward. The bastion becomes the single most valuable target in the whole design. A compromised bastion hands over the keys to everything behind it, and an unavailable one locks administrators out entirely. So the pattern only works with real monitoring, real redundancy, and the assumption that this one box will be under continuous attack.

Internet-facing vs private bastion designs

Classic bastions face the internet directly, ideally on an allowlisted public IP. AWS and Azure both offer managed bastion services now, brokering access through their own consoles (AWS commonly via an EC2 bastion pattern or Systems Manager), which removes the self-managed public listener from the equation entirely. Private bastions face only a VPN or peered network instead, trading internet exposure for dependence on the VPN layer. Every design here is headed the same direction: reduce or eliminate standing inbound listeners.

Bastion hosts vs RD Gateway

RD Gateway is Microsoft's productized take on the bastion pattern for RDP. Instead of hopping through a full desktop session, users tunnel RDP inside HTTPS through the gateway, which authenticates and forwards to internal hosts on their behalf. It removes the intermediate desktop and integrates cleanly with AD policy. It is still an internet-facing service, though, and needs the exact same hardening and patching discipline a manual bastion would. RD Gateway explained →

Bastion hosts vs Zero Trust RDP

The bastion pattern reduces exposure. A brokered Zero Trust pattern can eliminate it. A brokered model establishes sessions through outbound connections from inside the network, so no bastion or gateway listener has to face the internet. Access runs per identity and per resource instead of per network hop, and MFA plus least privilege replace what was really just network-location-based trust. Bastions still make sense where you genuinely need a self-contained hop. For routine remote desktop access, though, brokered Zero Trust RDP is the design that replaced it →