Definition
Broadcast isolation restricts the number of computers a host can contact on their LAN.
How it works
Software Defined Networking, or other network encapsulation technologies intercept host broadcast traffic then route it to a specified destination per a configured policy.
This can be implemented within hypervisors, networking hardware (WAPs, switches, routers), or virtual hardware.
Considerations
This technique is highly dependent on network infrastructure and networking requirements.
Implementation perspective
Broadcast Domain Isolation should be treated as a technical defensive capability rather than a product checkbox. In practice, teams should define the protected scope, the conditions under which the technique acts, and the observable evidence that demonstrates the intended behavior. For this technique, likely engineering context includes the relevant system, activity, and evidence sources.
Use the technique to create a logical or physical boundary that limits access, execution, communication, or movement.
Questions to ask
- What is being isolated, from whom or what, and under which conditions?
- Which flows or operations remain explicitly allowed across the boundary?
- What happens when the isolation mechanism fails or loses policy context?
- How is the boundary tested for alternate paths, bypasses, and unintended dependencies?
Evidence and validation
- Architecture and data-flow diagrams showing the isolation boundary
- Policy, rule, or configuration exports from enforcing components
- Tests of allowed, denied, and failure-state behavior
- Monitoring evidence for boundary violations and policy changes
Common failure patterns
- The intended boundary has undocumented alternate paths or inherited trust relationships.
- Rules accumulate without ownership, review, or removal of obsolete exceptions.
- Isolation is assumed from network location while application, identity, or management paths remain open.
This implementation perspective is original Bare Metal Cyber educational content. It does not replace the official D3FEND definition or establish that a specific product implements the technique.
Technique hierarchy
Top-level family
Parent techniques
Direct child techniques
None listed at this level.
Artifacts and ontology entities
These relationships describe how D3FEND connects a defensive technique to artifacts or other ontology entities. They describe graph semantics, not a product certification.
Explicit technique relationships
ATT&CK Enterprise mitigation relationships
These links come from the D3FEND ontology’s ATT&CK mitigation mapping. They help users navigate between the knowledge bases and do not guarantee mitigation effectiveness.
Authoritative sources
- Open this technique on the official D3FEND website ↗
- Open the official ontology resources ↗
- Broadcast isolation and level 3 network switch ↗Hewlett Packard Enterprise Development LP · Ballard C. Bare · PatentReference
- Private virtual local area network isolation ↗Cisco Technology Inc · Anuraag Mittal, Huei-Ping Chen · PatentReference
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