ExtremeSwitching (EXOS)

  • 1.  mirror avb traffic

    Posted 08-13-2015 19:19
    I'm trying to diagnose a problem with an AVB endpoint. I have a Summit X440-8t with the latest software build and the avb license pack. Three ports are connected: one to the endpoint module I'm trying to debug, one to a Windows PC running an application that sends and receives avb traffic to/from the endpoint, and a third connected to a Linux PC running Wireshark. I have configured a mirror on the switch to duplicate all ingress traffic on the port connected to the endpoint to the monitoring port connected to the Wireshark PC.

    When I set all of this going, I find that very little of the avb traffic actually ends up appearing on monitoring port, and the switch reports a high degree of congestion/packet loss on that port. There is no packet loss on either the port connected to the endpoint or on the port connected to the pc running the avb software - all 8000 packets per second appear to be flowing in both directions on these ports. But the number of packets appearing at the output of the monitoring port is of the order of a few 10s per second rather than the 8000 I might expect. The traffic that does turn up at the monitoring port has all the classes of packet I expect, but it seems to be dropping about 95% of the packets. This is puzzling (not to say more than a little frustrating).

    I'm not an expert on switches, protocols, or related technologies, but I thought I had understood enough to set up what seems to me to be a very straightforward test. There must be something very fundamental I'm missing. Any ideas what I could try?

  • 2.  RE: mirror avb traffic

    Posted 08-13-2015 19:51

    Is the mirror you have created enabled? You can check this with "show mirror"

    To enable:

    enable mirror

  • 3.  RE: mirror avb traffic

    Posted 08-13-2015 20:38
    quick response. Good job! Yes, I had enabled the mirror. When I disabled it again, I saw a drop in the packet rate from the mirror-to port, and an increase when I reenabled it. The port will have been configured as avb before I enabled the mirror, but would that explain the catastrophic rate of packet loss I'm seeing? If I understand correctly, the bug you referred to might result in additional unwanted packets appearing at the mirrored port, but that's not the problem I'm worried about at the moment. I guess the first thing I want to establish, complete novice that I am, is that what I'm trying to do (mirror all the 1722 packets to a monitor port) is actually possible. Is it? steve

  • 4.  RE: mirror avb traffic

    Posted 08-14-2015 07:21
    I tried again. I disabled the mirror, disabled avb on the mirror-to port, then re-enabled the mirror. This time it worked - all the expected traffic appeared on my monitoring port, and the switch is no longer showing any packet loss on any of the ports. All of which is entirely excellent - thank you very much for your help.

    I had come across the bug report prior to your message - the one about unexpected packets appearing at the mirror-to port, but I hadn't thought that it had much to do with the huge amount of packet loss I was seeing. Nevertheless, I had disabled avb on the mirror-to port and it didn't seem to make any difference. The trick, it appears, is to disable mirroring THEN disable avb, and finally re-enable mirroring.


  • 5.  RE: mirror avb traffic

    Posted 08-14-2015 11:24

    As far as I know, the congestion you experienced is a new symptom of this bug. I have updated our GTAC Knowledge article, adding the congestion as a symptom and modifying the resolution to include disabling/re-enabling the mirror.

    Updated article: AVB/Mirroring: AVB Control Protocol Traffic (gPTP, MSRP, & MVRP) transmitted from mirror-to port

    Thanks for your help!