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Catalyst 6500 Series Switch Command Reference—Release 8.4
OL-6244-01
Chapter 2 Catalyst 6500 Series Switch and ROM Monitor Commands
show port prbs
show port prbs
To display the ports that are running the Pseudo Random Binary Sequence (PRBS) test and to display
the counter values for ports on which the test has run, use the show port prbs command.
show port prbs [mod[/port]]
Syntax Description
Defaults This command has no default settings.
Command Types Switch command.
Command Modes Normal.
Usage Guidelines If you do not specify a mod value, the ports on all modules are shown. If you do not specify a port value,
all the ports on the module are shown.
The PRBS error counter measures the reliability of the cable. The error counter range is 0 to 255. A value
of 0 signifies a perfect link connection. A value of 255 signifies that the port is faulty or not connected
or that there is no communication through the link. If the counter does not remain at zero for a
predetermined length of time, the link is faulty. For example, for a baud error rate (BER) of 10^-12, the
counter should remain at zero for 100 seconds.
Each time you access the PRBS counter by entering the show port prbs command, the PRBS error
counter value is reset to 0, and the counter begins to accumulate errors again.
Note The PRBS counter is a “read and clear” register: the first reading in a sequence is usually unreliable and
serves primarily to purge the counter; successive readings are accurate.
Examples This example shows how to display PRBS counter values and the ports that are running the PRBS test:
Console> show port prbs
Max error counters = 255
Port PRBS state PRBS error counters
---- ----------------------------------
6/1 start 30
7/1 stop Console>
Related Commands test cable-diagnostics
mod (Optional) Number of the module.
port (Optional) Number of the port on the module.