Network Detection and Response (NDR) tools are only as good as the traffic you feed them. An NDR platform trained on incomplete data develops blind spots, and blind spots become the gaps that attackers exploit. If your NDR tool isn't seeing every packet, it isn't doing its job.
The problem is that getting complete, clean traffic to your NDR tool is harder than it sounds. Most organizations rely on Switched Port Analyzer (SPAN) ports to mirror traffic to monitoring tools, but SPAN ports drop packets under load, lack full-duplex visibility, and can't scale across large networks without significant compromise. The result is an NDR tool that processes an incomplete picture of your network, generating missed detections and false confidence.
The answer lies in building a purpose-built visibility layer using network TAPs and network packet brokers to capture, aggregate, filter, and deliver traffic to your NDR tool with zero packet loss. This article explains exactly how to do that.
NDR tools operate by analyzing raw network traffic to build behavioral baselines, detect anomalies, and identify threats. The detection quality depends entirely on the completeness and accuracy of the traffic stream they receive. Any gap in that stream is a gap in your detection capability.
NDR platforms analyze traffic at several levels to identify threats:
Every single one of these detection techniques requires a complete, uninterrupted traffic feed. A dropped packet doesn't just represent missing data. It can mean a missed command-and-control beacon, an incomplete flow record, or an undetected lateral movement event.
The most dangerous outcome of a poor traffic feed isn't a false positive. It's a false negative. When your NDR tool processes traffic with gaps, it still generates alerts, still produces reports, and still shows a dashboard that looks like everything is covered. Your security team assumes the tool is working. Meanwhile, threats in the blind spots go undetected.
This is why the visibility infrastructure feeding your NDR tool is just as critical as the NDR tool itself.
SPAN ports (also called mirror ports) are the default method many organizations use to send traffic copies to monitoring tools. They're built into most enterprise switches and seem like the obvious choice. But SPAN ports have fundamental limitations that make them unsuitable as the sole traffic source for a demanding tool like an NDR platform.
The most critical limitation is packet dropping. When a switch's central processing unit (CPU) becomes busy handling switching operations, SPAN port traffic is treated as low priority. During peak hours, exactly when a threat actor might be active, the switch starts dropping packets destined for the SPAN port to protect production traffic. Your NDR tool receives a partial picture of the traffic it needs to analyze.
SPAN ports can't flag which packets they've dropped, so your NDR platform has no way to know its data is incomplete. It continues analyzing the partial stream as if it were complete.
Beyond packet dropping, SPAN ports introduce several other problems:
These limitations compound in complex networks. When your NDR tool is supposed to monitor east-west traffic across dozens of internal links, SPAN-based approaches quickly become unmanageable.
A network test access point (TAP) solves the packet loss problem at its root. Rather than asking a switch to mirror traffic using spare CPU cycles, a TAP creates a physical copy of every packet on a link, completely independent of network device processing.
Passive fiber TAPs use optical splitters to divide the light signal on a fiber link into two streams: one continues to the original destination, the other goes to your monitoring infrastructure. There's no active processing involved, no CPU to overload, no logic that could drop a packet. The laws of physics guarantee the copy is made for every single packet.
Key characteristics of passive fiber TAPs relevant to NDR deployments:
For copper Ethernet links, Ethernet TAPs provide the same guaranteed capture capability. Active Ethernet TAPs regenerate the electrical signal and produce an accurate copy for your monitoring infrastructure. Modern active TAPs include fail-safe mechanisms that maintain the production link even if power is lost.
The combination of passive fiber TAPs and active Ethernet TAPs lets you achieve complete coverage across mixed-media networks without relying on SPAN ports for any critical segment.
Once you've deployed TAPs across your network, you face a new challenge: your NDR tool is a single appliance, but you have dozens or hundreds of TAP outputs generating traffic. You need a way to aggregate, filter, and intelligently distribute that traffic so your NDR tool receives exactly what it needs, at a rate it can process.
This is where a network packet broker becomes essential.
Consider a network with 20 monitored links, each running at 1Gbps. Each TAP produces two output streams (transmit and receive), so you have 40 streams of up to 1Gbps each. Your NDR tool has a single 10G input port. Without aggregation, you'd need 40 separate NDR tool inputs, which is neither practical nor affordable.
A packet broker solves this by aggregating all TAP outputs onto a high-speed backplane and forwarding consolidated traffic to your NDR tool. It manages the bandwidth math so your tool receives a complete, manageable traffic stream rather than an unworkable collection of individual feeds.
Not all traffic is relevant to your NDR tool. Backup jobs, video conferencing streams, and software update downloads generate enormous volumes of traffic that your NDR tool doesn't need to analyze for threats. Sending all of this to your NDR tool wastes processing capacity on low-value traffic and can push the tool toward its throughput limits.
A packet broker applies intelligent filters before forwarding traffic:
With targeted filtering, your NDR tool can analyze the traffic that matters without being overwhelmed by noise.
Beyond aggregation and filtering, packet brokers can pre-process traffic in ways that improve NDR tool performance and reduce storage requirements. This is particularly important for high-speed networks where NDR appliances can struggle to keep up with raw traffic volumes.
When traffic passes through multiple switches and TAP points in your network, the same packets often appear multiple times in your monitoring stream. These duplicates force your NDR tool to process the same conversation multiple times, consuming capacity that could be used on unique traffic.
Duplicate packets can account for a significant proportion of the total monitoring stream in complex networks with multiple TAP points. Removing them before delivery to your NDR tool is one of the most effective ways to extend the tool's effective capacity. The packet broker performs deduplication at line rate, transparently, before the traffic reaches your NDR appliance.
NDR tools typically analyze packet headers and flow metadata rather than full payload content. In many environments, forwarding only the first 256 bytes of each packet (or another configured slice depth) gives the NDR tool everything it needs for behavioral analysis while dramatically reducing the volume of data it must process.
The packet broker performs this slicing before forwarding, so your NDR tool receives compact, information-rich packets rather than full-size frames.
Some environments capture traffic that includes sensitive personal or financial data in packet payloads. Before forwarding this traffic to an NDR tool, a packet broker can mask payload content or strip unnecessary tunnel headers like Virtual Extensible Local Area Network (VXLAN) or Multiprotocol Label Switching (MPLS). This simplifies NDR analysis and supports data privacy compliance requirements.
A single NDR appliance may not have the processing capacity to handle all traffic from a large network. Many organizations deploy multiple NDR nodes to distribute the analysis workload. This creates a specific challenge: network sessions must be distributed across NDR nodes in a way that keeps the entire conversation together.
If you use simple round-robin load balancing to distribute traffic across three NDR appliances, the packets belonging to a single Transmission Control Protocol (TCP) session may end up on all three appliances. No single NDR node sees the complete conversation, so none of them can build an accurate behavioral baseline or detect session-level anomalies.
A packet broker with session-aware load balancing (sometimes called sticky or hash-based load balancing) solves this problem. It hashes a combination of source IP, destination IP, source port, and destination port to assign every packet belonging to a session to the same NDR node consistently. Each NDR appliance receives complete conversations, not fragments.
This approach lets you scale NDR capacity horizontally by adding appliances without compromising the analytical integrity that NDR detection depends on.
Putting these elements together produces a visibility architecture that reliably feeds your NDR tool with complete, clean, right-sized traffic. Here's how a well-designed deployment flows:
When selecting a packet broker for NDR feeding, consider these factors:
Modern enterprises don't run all their traffic through a single data center. Remote offices, cloud workloads, and OT networks all represent segments where your NDR tool needs visibility. A well-designed visibility architecture extends coverage across these environments.
For branch offices and remote sites, traffic can be captured locally using TAPs and forwarded to a central packet broker using Generic Routing Encapsulation (GRE) tunneling. The packet broker decapsulates the tunneled traffic and processes it alongside locally captured streams before forwarding to your NDR tool. This gives you centralized NDR visibility across distributed locations without deploying a separate NDR appliance at every site.
OT networks present specific challenges for NDR deployment. Active scanning or inline tools can disrupt sensitive industrial control systems, making passive TAP-based capture the only safe approach. TAPs on OT network segments feed traffic to the packet broker without any active interaction with the OT devices themselves, giving your NDR tool visibility into industrial network behavior without operational risk.
Some NDR deployments run in inline mode, with traffic passing through the NDR appliance rather than being delivered as a copy. In this configuration, bypass TAPs become essential. A bypass TAP monitors the health of the inline NDR appliance and automatically switches traffic around it if the appliance fails, goes offline for maintenance, or becomes overloaded. Your production network stays up even if the NDR tool experiences an issue.
Yes, and in practice many organizations do this during a transition period. SPAN ports can supplement TAP-based feeds for lower-priority segments, but you should never rely on SPAN ports for segments where complete visibility is critical. Use TAPs for any link where a missed packet could mean a missed detection.
Filtering does introduce the possibility of excluding traffic that matters, so filter configurations require careful thought. The safest approach is to start with inclusive filters (forward everything from monitored subnets) and gradually refine them based on what your NDR tool flags as noise. Avoid aggressive filtering until you understand your traffic patterns well.
Quality packet brokers include redundant power supplies and fail-safe TAP modules that maintain monitoring continuity during hardware faults. For passive fiber TAPs, the monitoring copy disappears if the TAP's monitor output loses power, but the production link stays up. Designing for redundancy at the packet broker level protects both your production network and your monitoring continuity.
For most NDR use cases, no. NDR tools analyze headers, flow metadata, and behavioral patterns rather than payload content. Slicing to 256 bytes typically preserves all the header information the tool needs. If your NDR tool also performs payload inspection for data loss prevention or malware detection, you'll need to deliver full packets to that specific tool while still slicing for other consumers of the same traffic.
Building a reliable traffic feed for your NDR tool requires purpose-built visibility infrastructure designed specifically for zero packet loss and flexible traffic management. Network Critical has provided network visibility solutions to enterprises and government networks since 1997, helping organizations achieve complete traffic coverage without compromising network performance or security.
Our passive fiber and active Ethernet TAPs guarantee packet capture at every monitored link, passing full-duplex traffic including physical layer errors to your monitoring infrastructure. For organizations running inline NDR tools, our bypass TAPs protect production network availability by automatically switching traffic around any inline appliance that fails or goes offline.
The SmartNA-PortPlus family of network packet brokers provides the aggregation, filtering, deduplication, and session-aware load balancing your NDR deployment needs, all manageable through our intuitive Drag-n-Vu interface. Whether you're feeding a single NDR appliance from a small campus network or scaling out NDR across a distributed enterprise, our team can help you design a visibility architecture that delivers every packet your NDR tool needs to do its job.