Show port Utilization command

[Alex23]

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.

[Alex23]

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.

[Sumit_Tokle]

Multicast or brodcast packet might be sent out from this port. Please confiugre mirroring and see what packets are going out.

[Jason3]

Alex 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 Jason

[Alex23]

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

[rbrt]

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,
Robert