Drops TX - how to identify source or reason

[Danniel_Simoni]

Hello all.

Having an issue with one of my local segments.  It's pretty straightforward from a design standpoint. I have a top-of-rack 2910-al , and it's interconnected to (9) 2620-48 switches. The ToR has port 1 connected to the gateway router, and each 2620 has the gbit port connected to the ToR , and the rest of ports go to clients. The ToR has zero errors on all ports - clean and pristine.

But, each of the 2620s have a ton of "Drops TX" - this is on every port (except the gbit uplink to the ToR). An example of number of drops is (i just selected a random port)

total bytes = 2,119,692,994
Drops TX = 2,885,969

The users are not reporting issues, but there is clearly an issue somewhere. But, I don't know where to begin in tracking it down. I have spanning tree turned on for this segment, with the ToR being the root, no ports have been disabled.

Any troubleshooting ideas would be greatly appreciated.

Thanks

[Vince-Whirlwind]

Do you have a network monitoring product? You need to check out utilisation on each of the 2620 switchports.

One case where I have seen this is where one of the servers is originating traffic using a source address that is actually advertised from a different physical NIC, causing the switch to flood the return traffic out all ports - if the return traffic is coming from a host that is using a 1Gb port, then all 100Mb ports on the segment will show dropped packets as a result.

[BCS_maddog]

I have a similar, but almost opposite, issue with my 2910al.  I have no errors on any of the ports except for the uplink port to the core switch/router.  My Drops Tx is close to 25%.  I've read a lot of older posts stating the buffers are being filled, etc, but how do you tell?  My monitoring software is telling me the links are nowhere close to full utilization (150Mb on a 1Gb port).   The user experience is that file transfers that traverse this link run slow, if they even complete at all.

                      Status and Counters - Port Counters

                                                                     Flow   Bca*
  Port    Total Bytes     Total Frames    Errors Rx      Drops Tx    Ctrl   Lim*
  -----  --------------  --------------  ------------  ------------  -----  ---*
  1         601,786,974   3,736,432,518             0   924,047,362  off    0

[jjalonsom]

Hi, did you find a solution?

It could be caused for a bad cable?