Port Monitoring
Port Monitoring
An essential tool of the network engineer is a network packet capture device. A packet capture device is
usually a PC-based computer, such as the Sniffer
ing data traffic of a network. Understanding data flow in a VLAN-based switch presents unique chal-
lenges, primarily because traffic moves inside the switch, especially on dedicated devices.
The port monitoring feature allows you to examine packets to and from a specific Ethernet port. Port
monitoring has the following features:
•
Software commands to enable and display captured port data.
•
Captures data in Network General
•
A file called pmonitor.enc is created in the /flash memory when you configure and enable a port
monitoring session.
•
Data packets time stamped.
•
One port monitored at a time.
•
RAM-based file system.
•
Statistics gathering and display.
The port monitoring feature also has the following restrictions:
•
All packets cannot be captured. (Estimated packet capture rate is around 500 packets/second.)
•
The maximum number of monitoring sessions is limited to one per chassis and/or stack.
•
You cannot configure a port mirroring and a port monitoring session on the same NI module in an
OmniSwitch 9000.
•
You cannot configure port mirroring and monitoring on the same switching ASIC on OmniSwitch
6850 Series switches. Each switching ASIC controls 24 ports (e.g., ports 1–24, 25–48, etc.). For exam-
ple, if a port mirroring session is configured for ports 1/12 and 1/22, then configuring a port monitor-
ing session for any of the ports between 1 and 24 is not allowed.
•
You cannot configure port mirroring and monitoring on the same switching ASIC on OmniSwitch
6800 Series switches. Each switching ASIC controls 12 ports (e.g., ports 1–12, 13–24, etc.). For exam-
ple, if a port mirroring session is configured for ports 1/6 and 1/10, then configuring a port monitoring
session for any of the ports between 1 and 12 is not allowed.
•
If a port mirroring session is configured across two switching ASICs, then configuring a monitoring
session is not allowed on any of the ports controlled by each of the ASICs involved. For example, if a
port mirroring session is configured for ports 1/8 and 1/30 on a 48-port switch, then configuring a port
monitoring session involving any of the ports between 1 and 48 is not allowed.
•
Only the first 64 bytes of the traffic will be captured.
•
Link Aggregation ports can be monitored.
•
If both mirroring and monitoring are enabled, then packets will either be mirrored or monitored (i.e.,
sent to CPU), whichever comes first. See
mation.
You can select to dump real-time packets to a file. Once a file is captured, you can FTP it to a Sniffer or
PC for viewing.
page 35-24
®
, that provides a means for understanding and measur-
®
file format.
"Mirroring on Multiple Ports" on page 35-15
OmniSwitch 6800/6850/9000 Network Configuration Guide
Diagnosing Switch Problems
for more infor-
March 2008