# What is a Distributed Firewall?

> A distributed firewall is a non-standard architectural label for coordinated firewall policy enforced at multiple points rather than only at a central appliance.

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## Content

Enforcement may run in host agents, hypervisors, virtual switches, cloud controls, workload gateways, or other points near protected resources, while policy and telemetry may be managed through a shared control plane.

This design can control traffic that never crosses a traditional perimeter, including communication between workloads on the same host or cloud network. Policy may use network attributes, workload or service identity, tags, and platform context. Implementations vary in whether control is centralized, how rules are compiled, and which enforcement points remain authoritative during disconnection.

### Key points

- **Coverage design:** Map workloads and communication paths to enforcement points, include temporary and unmanaged assets, and identify paths that bypass agents, overlays, or virtual switching controls.
- **Policy lifecycle:** Use consistent identity and asset data, stage changes, detect conflicts, verify propagation, remove stale rules, and reconcile platform-specific behavior with the intended policy.
- **Resilience and assurance:** Protect the control plane and credentials, define fail-open or fail-closed behavior, monitor enforcement health, preserve local operation where required, and test recovery from partial deployment.
- **Important limitation:** Distribution does not guarantee uniform or least-privilege enforcement. Missing agents, stale policy, inconsistent labels, compromised management, unsupported traffic, or overlapping cloud and network rules can create gaps that a central policy view does not reveal.

### Related terms

[Firewall](<https://yellowcube.eu/glossary/firewall/>) · [Virtual firewall](<https://yellowcube.eu/glossary/virtual-firewall/>) · [Cloud firewall](<https://yellowcube.eu/glossary/cloud-firewall/>) · [Microsegmentation](<https://yellowcube.eu/glossary/microsegmentation/>) · [Zero trust architecture (ZTA)](<https://yellowcube.eu/glossary/zero-trust-architecture/>)

### Sources

[NIST glossary: Distributed Firewall](https://csrc.nist.gov/glossary/term/distributed_firewall) · [NIST SP 800-125B: Secure Virtual Network Configuration for VM Protection](https://csrc.nist.gov/pubs/sp/800/125/b/final) · [NIST SP 800-41 Rev. 1: Guidelines on Firewalls and Firewall Policy](https://csrc.nist.gov/pubs/sp/800/41/r1/final)

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