How Probes Work With Switches - Network Instruments GigaStor User Manual

3)
Only available on hardware probes from Network Instruments.
4)
Decoding and expert analysis are performed by the probe and a summary is sent to the Observer analyzer reducing network
bandwidth use.
5)
Application Performance Analysis and Application Transaction Analysis. Applications are generally OSI Layer7 applications
like HTTP, FTP, RTSP, SMB, and so on.

How probes work with switches

The purpose of a switch is to isolate traffic to the local network, thereby reducing the amount of traffic each
device on that network must see and process. Although a protocol analyzer puts a network interface card
in "promiscuous" mode, the analyzer only sees packets addressed to or transmitted from the port that it is
connected to on the switch.
To operate a probe in a switched environment, you must choose a method that provides network visibility to
the port where the probe is connected. Most switches provide a function that "mirrors" all packets received or
transmitted from either a single port of interest (for instance, a server or router), or multiple ports of interest. The
mirrored traffic can then be captured or analyzed by connecting your analyzer (or in this case, the probe) to the
"mirror port" (which is sometimes called a SPAN port).
Switches typically provide two options for configuring the SPAN/mirror port settings. You can either use a
command line interface (CLI) or web-based interface included with your switch to set the port (or ports) to be
mirrored.
To SPAN/mirror ports, Observer can use SNMP to directly query your switch and report port-based statistics
or use RMON to report any internal RMON statistics the switch may have. Selecting the method right for you
depends on your switch, and the level of detail you need to troubleshoot the problem at hand. For packet
capture, decode and Expert Event identification, only static port mirroring provides all the information required
for a complete picture of what is happening on your network.
22 | GigaStor™ (pub. 25.Apr.2014)