Show port Utilization command

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Hello, I have a question regarding the way Extreme switches display traffic direction on its ports.

We have a GPS/weather-receiver station connected to one of our switches (Summit X450e) that transmit data only one way (from the GPS unit to our network). Thus, I'd expected to see traffic going 'into' the switchport and nothing else. However, when I issue a 'sh port 1:44 utilization' command I get the total opposite, with traffic being transmitted 'from' the switchport instead of 'to' the switchport. Am I reading this wrong? Please see output below:

Slot-1 MySwitch# sh por 1:44 utilization 
Link Utilization Averages                            Thu Aug 14 14:17:13 2014Port     Link    Rx              Peak Rx          Tx               Peak Tx
         State   pkts/sec        pkts/sec         pkts/sec         pkts/sec
GPS_Unit  A             0              0                7              10

Any input is appreciated. Thanks.
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Posted 4 years ago

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Jason, Employee

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Is ther a way that you can place a repeater between the port and the station and then place a sniffer ( Wireshark is free) and capture traffic
I would the note the MAC address of the station and type
Eth.addr == xx-xx-xx-xx-xx-xx
Then reveiw the traffic
Another step
!Eth.addr == xx-xx-xx-xx-xx-xx
And review that traffic
Please relay your findings

Or just configure mirror Oh My God to a drat port and run the same commands
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Ok Jason, I will try to mirror the port where the GPS is connected. Hopefully those Wireshark filters will reveal more.. thanks.
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Hi Alex,

I'd say that this is totally fine, because broadcasts for example are transmitted out of every port - including the one where you've connected your GPS unit. Basically you should see traffic from the switch to the end device on every port that is active.

The switch does not know that your GPS unit does not want to receive traffic. If you want to make sure that no traffic reaches the GPS unit, you have to write an ACL denying every bit of traffic that goes to the GPS unit.

Hope that helps,
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Well, that makes sense except that the Rx packet count is 0. I'm only seeing transmits on that port
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Jason, Employee

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I agree with Robert that once you review the traffic and find unwanted traffic then build an ACL
You can also check the source and shut them down if needed
Let us know if you need more assistance
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Sumit Tokle, Alum

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Multicast or brodcast packet might be sent out from this port. Please confiugre mirroring and see what packets are going out.
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Yes, I will try mirroring next Sumit. But I'm still not understanding the way Extreme switches report port utilization. When you do a sh por ut ... does the Tx column mean traffic going out of that port into the plugged end device? Or is it the opposite? Thanks.
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Daniel Flouret, Employee

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Show port utilization displays packets per second. If the GPS does not transmit frequently, this might show as 0 pps...

Have you tried using show ports statistics, which shows the number of packets transmitted and received?

And regarding your question as to what does Tx and Rx stand for, remember that the documentation is your best friend (in the old days we used to say RTFM, but that's a bit rude by today's standards... hahaha)

From the description of the show ports statistics command in EXOS Command Reference Guide for Release 15.3.2, page 1069:

Collected Port Statistics
The switch collects the following port statistic information:
• Port Number
• Link State—The current state of the link. Options are:
• Active (A)—The link is present at this port.
• Ready (R)—The port is ready to accept a link.
• Not Present (NP)—The port is configured, but the module is not installed in the slot (modular
switches only).
• Loopback (L)—The port is in Loopback mode.
• Transmitted Packet Count (Tx Pkt Count)—The number of packets that have been successfully
transmitted by the port.
• Transmitted Byte Count (Tx Byte Count)—The total number of data bytes successfully transmitted
by the port.
• Received Packet Count (RX Pkt Count)—The total number of good packets that have been received by the port.
• Received Byte Count (RX Byte Count)—The total number of bytes that were received by the port,
including bad or lost frames. This number includes bytes contained in the Frame Check Sequence
(FCS), but excludes bytes in the preamble.
• Received Broadcast (RX Bcast)—The total number of frames received by the port that are addressed to a broadcast address.
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Daniel, I have reviewed the Command Reference Guide and could not find the answer... that's why I posted it here. The show ports statistics command is consistent with what I found on the show ports utilization command... I know that the GPS only transmits one-way (from the GPS unit to the port). However, the switch is reporting the packets being transmitted on that switchport port, not received. Unless Extreme meant that the 'Tx' on the show port statistics means 'packets transmitted to this port' instead of 'packets transmitted to this port'.