What Is Network Segmentation and Why It Matters

Types of network segmentation

Network segmentation creates discrete zones that separate different users, devices, applications, or traffic flows. This is accomplished through several means:

• Physical Segmentation. This involves using actual network hardware like routers, switches, and firewalls to physically divide a network. It provides the highest level of isolation.
• Logical Segmentation. This utilizes virtual networking techniques like virtual local area networks (VLANs) and Layer 3 IP addressing schemes to divide networks without requiring new equipment. VLANs configure switch ports into isolated traffic groups, while Layer 3 assigns devices IP addresses on different logical subnets, enforcing separation through a router. Software-defined networking (SDN) is also used for logical segmentation.
• Internal Firewalls and Access Control Lists (ACLs). These enforce policies between segments, controlling traffic flow and preventing unauthorized lateral movement. ACLs define rules based on criteria like IP addresses, port numbers, and protocols.

Network segmentation vs. microsegmentation

While network segmentation and microsegmentation are often used interchangeably, they represent different approaches to network security with distinct scopes and implementation strategies.

• Traditional Network Segmentation. This operates at a broader level, dividing networks into larger zones based on organizational boundaries such as departments or business functions. This approach creates perimeter-based security zones using subnets, VLANs, or physical infrastructure.
  
  For example, separating the finance department from marketing, or isolating guest networks from corporate resources. Security controls are applied at the segment level with traffic inspection at defined entry and exit points.
• Microsegmentation. This takes a more granular approach, creating highly specific security zones around individual applications, workloads, or devices. This strategy operates primarily through software-defined policies, enabling administrators to apply security controls at the workload level. Microsegmentation can isolate a single database server or specific application instance within the same physical network segment.

The key differences lie in implementation and scope. Network segmentation relies on network infrastructure and creates broader security boundaries, making it easier to implement. Microsegmentation leverages SDN and identity-based policies for precise, dynamic security boundaries.

The approaches are complementary rather than competing strategies. Many organizations implement traditional network segmentation as a foundation and layer microsegmentation on top for enhanced protection where needed.

Network segmentation use cases

Network segmentation is employed in a wide array of practical scenarios to enhance both security and operational efficiency within complex digital environments. Organizations implement network segmentation to improve security, monitoring, access controls, and network performance.

Here are a number of top use cases for network segmentation:

• Securing Guest Wi-Fi Access. Organizations can segment guest access by creating a separate guest Wi-Fi network with its own distinct service set identifier (SSID). This allows visitors to have internet access while remaining isolated from internal company resources or data.
  
  Enabling wireless isolation for the guest SSID contains all their traffic within an isolated virtual segment, minimizing the attack surface. This is considered a crucial step, as allowing guests access to corporate Wi-Fi can be risky due to unknown and untrusted devices.
  
  Even residential routers often include this feature. One VLAN, for example, could allow basic guest Wi-Fi access while keeping guests from seeing or interacting with devices on other networks.
• Departmental and User Group Segmentation. Segmenting different user groups or departments based on their data access needs adds a layer of protection for each department on the network. This means user groups, such as different departments or teams, can operate in separate segments with their own access controls and security policies, even if they share the same hardware.
  
  For instance, a hospital can segment its medical devices from its visitor network to ensure medical devices are unaffected by web browsing. Access between these subnets is rigorously controlled. For example, an attempt by someone in engineering to access the human resources subnet would trigger an alert and an investigation. One VLAN could segment off an accounting department.
  
  By limiting users' access privileges to only those who need them, segmentation safeguards the network against widespread cyberattacks and improves performance by reducing user density.
• Isolation of Critical Applications and Sensitive Data. Different business applications often have varying security needs, and segmentation allows for customized security measures for each.
  • Sensitive Data Isolation. Highly sensitive data, like employee salaries and bank details in a payroll system, can be isolated into specific segments with stricter access policies, more frequent audits, and tighter backups. Similarly, customer databases, due to compliance requirements, need more intense security than, for example, a print server.
  • Application-specific Servers. Organizations can create separate segments for application-specific servers. This can limit malware from crawling between applications. For instance, a bank's financial reporting system can be segmented to prevent general branch employee access, ensuring it works better for financial analysts.
  • Payment Card Industry Data Security Standard (PCI DSS) Compliance. Segmentation is vital for isolating all credit card information into a security zone to comply with regulations, allowing only the absolute minimum, legitimate traffic into the zone while automatically denying everything else. This approach helps reduce the costs associated with regulatory compliance by limiting the number of in-scope systems.
• Protection of Specialized Devices and Systems. Segmentation can prevent harmful traffic from reaching devices that lack advanced security defenses or require dedicated performance.
  • Voice Networks (VoIP/Communications). Voice traffic is sensitive to jitter and latency. By segmenting voice users into a dedicated VLAN, the infrastructure can be optimized for reliable voice delivery, and quality of service (QoS) policies can prioritize voice packets to avoid choppy calls. Mixing voice and data on the same network often introduces problems.
  • Medical Devices. Hospitals can deploy network segmentation to protect medical devices, such as connected infusion pumps, from attacks, stopping harmful internet traffic from reaching them.
  • Physical Security Systems. Cameras, ID card scanners, and other traditional physical security systems should be placed in their own network zone, as a physical breach can be as harmful as a digital one.
  • Industrial Control Systems (ICS). These systems are common points of attack and should be segmented from each other and the corporate data network.
  • Internet of Things (IoT) Devices. Segmentation protects endpoint devices as IoT devices become more common. Network access control (NAC) solutions can assist with managing IoT devices, limiting areas of the network they can access.
  • Autonomous Warehouse Robots. These require ultra-low latency to navigate properly, and segmentation can apply a customized QoS to their network segment.
• Secure Privileged Access and IT Workstations. Highly privileged accounts, such as domain administrators, can be segmented into confined network zones to restrict damage if their credentials are ever compromised.
  
  For example, domain controllers and admin workstations can be isolated into a separate management subnet with additional monitoring and controls. This also streamlines logging and auditing of admin activity to detect suspicious actions.
  
  IT can also be given their own network segments for testing, development, and management, with very specific controls to manage risks.
• Demilitarized Zone (DMZ) Subnets. Segmentation is used to create a DMZ subnet for externally facing systems, such as public-facing websites or other internet-accessible resources. This separates public-accessible resources from the internal local area network (LAN) data that needs protection.
• Public and Hybrid Cloud Security. Segmentation is an effective method for isolating applications in public and hybrid cloud environments. In hybrid and multicloud environments, where physical separation is not practical, logical segmentation approaches like VLANs, subnets, or SDN are especially useful, allowing different cloud providers to be assigned their own virtual segments.
  
  Organizations are responsible for the security of operating systems, platforms, access control, data, and intellectual property that sit atop cloud infrastructure, making segmentation crucial.
• Mergers and Acquisitions (M&A). When companies merge or acquire other organizations, directly connecting their networks poses significant security risks due to potential inherited vulnerabilities. Network segmentation allows organizations to maintain separation between the networks during integration, enabling a gradual, careful pace of uniting them.
  
  Connectivity between segments should be selectively enabled only after thorough penetration testing, policy reviews, and risk assessments.
• General Network Performance Enhancement. Segmentation generally contributes to better network performance across the board. Benefits include:
  • Reduced Congestion. Smaller subnets mean fewer hosts, less traffic, and a smaller broadcast domain, which reduces "noise" and network congestion. This ensures critical applications receive necessary bandwidth.
  • Optimized Traffic Flow and Resource Allocation. Segmentation allows for more strategic resource allocation and better traffic control by separating different types of traffic (e.g., internal vs. external, voice vs. data). This allows organizations to prioritize critical data flows.
  • Reduced Latency. Isolating bandwidth-heavy activities means essential services do not compete for the same resources, reducing delays and improving user experience. This is particularly important for resource-intensive services like online gaming, media streaming, and videoconferencing.
  • Quality of Service (QoS). Segmentation makes it easier to build and enforce granular QoS policies. It enables administrators to create different networks for each use case and then apply a customized QoS to that group, which is easier to implement and troubleshoot than applying policies at the device level.

Security benefits of network segmentation

Network segmentation is primarily applied as a security measure, creating boundaries that limit an attacker's ability to move laterally within the network. It is considered a critical component of network security due to its effectiveness in mitigating potential risks and minimizing the severity of security incidents.

Key security enhancements include:

• Reduced Attack Surface. By dividing the network into smaller segments, each with its own dedicated resources and security controls, network segmentation significantly shrinks the blast radius of an attack. If one part of the internal network or cloud environment is compromised, other segments remain secure. This makes it harder for attackers to reach critical systems as they need to bypass multiple segmented layers.
• Improved Breach Containment. Breaches are confined to specific segments, preventing attackers from moving laterally and accessing other parts of the network. This limits the spread of malware and reduces the damage and exposure, making remediation efforts more efficient. For example, a malware outbreak in one section would not impact systems in another.
• Enhanced Data Security and Protection of Critical Assets. Segmentation protects sensitive information by isolating it into specific segments, making it harder for attackers to access. It allows for tailored security measures and access control policies within each segment, ensuring that only authorized personnel can access sensitive data.
• Better Access Control. Administrators can set granular permissions based on user roles, devices, or application requirements, ensuring that only authorized entities can access specific segments. This reduces the risk of unauthorized access and helps maintain network integrity.
• Improved Monitoring and Threat Detection. Segmentation allows for more points in the network where traffic can be inspected, counted, and monitored. It provides a comprehensive view of traffic patterns and behaviors within each segment, making it easier to pinpoint anomalies and detect threats. Segmenting subnets simplifies monitoring traffic flow, reducing the chances of a threat being missed.
• Streamlined Incident Response. Clear segmentation allows for faster detection of which part of the network is compromised, enabling quicker prioritization of response efforts. Affected areas can be quickly isolated, preventing further spread and minimizing impact.
• Integration with Zero Trust. Network segmentation is a critical enabler for Zero Trust architecture, which assumes nobody is trustworthy by default, even those inside the network perimeter. It helps implement a Zero Trust Strategy by limiting what is accessible to any user or device at any time, effectively trapping an attacker within a compromised segment and preventing lateral movement to more sensitive systems. This approach rigorously isolates sensitive assets and monitors them closely.
• Reinforced Regulatory Compliance. Segmentation aids in maintaining regulatory and cyber insurance compliance by creating boundaries for sensitive data and implementing necessary security measures for each segment. By segregating sensitive data, organizations can easily identify and manage systems within compliance scope, reducing complexity and costs.

Challenges of network segmentation

Network segmentation can complicate visibility and monitoring by creating multiple traffic inspection points across different segments. Organizations often struggle to maintain comprehensive visibility and detect threats that span multiple network zones.

To address this challenge, deploy network detection and response (NDR) solutions that provide centralized monitoring across all segments, such as Trellix Network Detection and Response.

Implement unified logging and security information and event management (SIEM) systems to correlate activities across network boundaries, ensuring complete visibility into network-wide security events.

Emerging trends in network segmentation

Network segmentation continues to evolve with technological advances and changing security landscapes, driving several key trends that are reshaping how organizations approach network security.

• AI-driven Segmentation. This is revolutionizing traditional approaches by using machine learning algorithms to automatically identify optimal segmentation boundaries based on traffic patterns, user behavior, and risk assessments. AI systems can dynamically adjust segment policies in real-time, responding to emerging threats and changing network conditions without manual intervention.
• Zero Trust Network Access (ZTNA). This integration is becoming standard practice, moving beyond traditional perimeter-based segmentation to identity-centric models. This approach treats every network segment as potentially compromised, requiring continuous verification and authentication regardless of location within the network.
• Cloud-native Segmentation. This addresses the unique challenges of hybrid and multi-cloud environments. Container-based segmentation using technologies like Kubernetes network policies enables granular control over microservices communications, while cloud security posture management (CSPM) tools provide consistent segmentation policies across diverse cloud platforms.
• Intent-based Networking (IBN). This allows administrators to define high-level security policies in business terms, which are then automatically translated into technical network configurations. This approach simplifies policy management while ensuring alignment between business requirements and technical implementation.

These trends indicate a shift toward more intelligent, automated, and adaptive segmentation strategies that reduce administrative overhead while enhancing security effectiveness.

In summary, network segmentation is a fundamental cybersecurity strategy that divides a larger network into smaller subnetworks to enhance security, control access, improve performance, simplify management, and aid regulatory compliance by isolating critical systems and data flows.