TAP vs. Span: What’s the Difference...and Does it Matter?

A network test access point (TAP) and port mirroring (aka SPAN) are the two most common access methods of packet capture for the use of analysis in data monitoring. Is there a difference? Yes, there are significant differences which affect the integrity of the traffic that is being analyzed, as well as the performance of the network traffic. This page discusses the differences in regards to monitoring the network, when deploying and managing active, in-line appliances SPAN should never used as packets are randomly dropped when the SPAN ports become oversubscribed.

TAP - Network Test Access Point

A hardware tools that allows you to access and monitor your network. TAPs transmit both the send and receive data streams simultaneously on separate dedicated channels, ensuring all data arrives at the monitoring device in real time.

  • Court approved - a TAP provides forensically sound data/evidence that data captured is 100% accurate with time reference.
  • TAPs do not alter the time relationships of frames, spacing and response times especially important with VoIP and Triple Play analysis including FDX analysis.
  • Fiber TAPS are 100% passive and have no power.
  • Network TAPs have no IP address, no MAC address and cannot be hacked.

SPAN - Switch Port for Analysis

Port Mirroring also known as SPAN (Switched Port Analyzer), sends a copy of all network packets seen on one port (or an entire VLAN) to another port, where the packets can be analyzed.

  • SPAN sessions do not interfere with the normal operation of the switch.
  • Remotely configurable from any system connected to the switch.
  • Disallows bidirectional traffic on that port to protect against backflow of traffic into the network.


Want to dig deeper? Read Garland Technology's TAP vs SPAN white paper.

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Enjoy our latest edition of:

TAP Toons: The Student has become the Network Master - Part 1

Read the full post here.

TAP Toons: The Student has become the Network Master - Part 2

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To learn more about using TAP vs SPAN, download our free white paper: TAP vs SPAN Real Network Visualization - Consideration for Professionals.