Cabletron Systems STS16-20R - Manual (Page 225)

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Monitoring Port Traffic SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide
9. Monitoring Port Traffic
The SmartStack STS16-20D/STS16-20R allows you to configure a Switched Port
Analyzer function for monitoring traffic on a port. An analyzer port is a port on
which an external probe can observe traffic from any other port, that is a monitored
port. The monitoring function is does not interfere in any way with the normal
traffic flow in the switch.
The external probe (for example, a protocol analyzer) is not supplied with the
switch.
You can monitor traffic going through a monitored port in two different ways, by
using either:
•
active monitoring or
•
passive monitoring.
Active Monitoring
This mode copies traffic switched to and from the monitored port to the analyzer
port. Since MAC frames never are switched between ports, they will not be seen on
the analyzer port. To prevent spurious frames, the analyzer port must be a Token-
Ring port on the same box as the monitored port. It is recommended that you put
the analyzer port into a separate VLAN. The monitored port can be any type of port
(Token-Ring, ATM, HSTR, and Fast Ethernet)
➽ Note! The analyzer port works as a normal port. This means it can be in FDX/HDX
mode, Station/Port 4 or 16 Mpbs. Moreover, you can use any external probe. The
frames will be buffered normally, that is, if you try to monitor a FDX 16 MB line
with a 4 MB HDX port, data loss can occur.
When the monitored port is in HDX mode, the frames sent to the analyzer port will
be the frames received on the Token-Ring of the monitored ports (that is, a true
copy apart from MAC frames). When monitoring a FDX port, it is the forwarding
port that is responsible for the copy. As a consequence, packets may be seen on the
analyzer port in a different order than on the monitored port. Moreover, since it is
the monitored port itself that expands Source Route Explorer frames, the last ring
and bridge number will be missing from explorer frames passing a BRF in the
switch.
Passive Monitoring
This mode makes a physical connection from the monitored port to the analyzer
port. Both the monitored and the analyzer port must be Token-Ring ports. You can
choose to connect either the transmit or the receive wire from the monitored port to
the analyzer port. That is, if the monitored port is in HDX mode, the analyzer port