ExtremeSwitching (EXOS)

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STP topology changes

  • 1.  STP topology changes

    Posted 08-10-2017 15:20
    I've been trying to track down an issue with STP in one of our branch offices, for some reason STP has an immense amount of STP changes logged;

    i.e
    Topology Change Detected: FALSE Topology Change: FALSE

    Number of Topology Changes: 4974700

    Time Since Last Topology Change: 42s

    It's worth to note that we have a mixed environment with HP's and EXTREME's, does this config look correct ?
    Stpd: s1 Stp: ENABLED Number of Ports: 46

    Rapid Root Failover: Disabled

    Operational Mode: 802.1W Default Binding Mode: EMISTP

    802.1Q Tag: (none)

    Ports: 1:1*,1:3,1:4,1:5,1:6,1:7,1:8,1:9,1:10,1:11,

    1:12,1:13,1:14,1:15,1:16,1:17,1:18,1:19,1:20,1:21,

    1:22,1:23,1:24,2:1*,2:3,2:4,2:5,2:6,2:7,2:8,

    2:9,2:10,2:11,2:12,2:13,2:14,2:15,2:16,2:17,2:18,

    2:19,2:20,2:21,2:22,2:23,2:24

    Participating Vlans: Default

    Auto-bind Vlans: Default

    Bridge Priority: 28672

    BridgeID: 70:00:02:04:96:51:b9:fd

    Designated root: 70:00:02:04:96:51:b9:fd

    RootPathCost: 0 Root Port: ----

    MaxAge: 20s HelloTime: 2s ForwardDelay: 15s

    CfgBrMaxAge: 20s CfgBrHelloTime: 2s CfgBrForwardDelay: 15s

    Topology Change Time: 35s Hold time: 1s

    Topology Change Detected: FALSE Topology Change: FALSE

    Number of Topology Changes: 4974700

    Time Since Last Topology Change: 192s


    ON AN HP:
    HP-2848-LA-CAR-R8-1# show spanning-tree

    Rapid Spanning Tree (RSTP) Information

    STP Enabled : Yes

    Force Version : RSTP-operation



    Switch Priority : 32768 Hello Time : 2

    Max Age : 20 Forward Delay : 15



    Topology Change Count : 405,614

    Time Since Last Change : 4 mins



    Root MAC Address : 020496-51b9fd

    Root Path Cost : 22000

    Root Port : 43

    Root Priority : 28672

    Any ideas?



  • 2.  RE: STP topology changes

    Posted 08-10-2017 23:06
    1. Are we seeing any continuous port flaps between these switches on active port# 1:1, 2:1 ? If yes, did you try to eliminate the cable issues or any other symptom triggering the topology change?
    2. Is it new implementation or any recent configuration/firmware changes made?
    3. Provide us the "show configuration stp" and "top" output.
    4. What is the current EXOS version and switch type?
    5. Is there any suspicious logs generated in switch?
    6. Did you configure edge ports?

    The configuration on Extreme device looks fine.

    The below link gives you the basic idea of configuring RSTP in Summit/BlackDiamond switches:
    https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-configure-RSTP-in-EXOS?_ga=2.148314807.1012568893.1502325830-1247773174.1501480829

    The below link is for the user guide to EXOS and sample configuration is available for your reference: https://extrcdn.extremenetworks.com/wp-content/uploads/2014/01/EXOS_Concepts_Guide_15_4.pdf?_ga=2.171259424.1012568893.1502325830-1247773174.1501480829



  • 3.  RE: STP topology changes

    Posted 08-14-2017 10:49
    Hi Tom,

    Please bear in mind that if the user ports of HP switch are not configured for edge port (or PortFast in Cisco terms) then each time a PC disconnects/connects you will get a Topology change. So you should configure edge ports on both switches' user ports.

    Also, you can prevent the ARP entries from being cleared when a TC occurs by enabling iparp fast-convergence. Please see below article.
    https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-prevent-topology-change-impact-on-r...



  • 4.  RE: STP topology changes

    Posted 08-14-2017 21:23
    Hi Tom,

    Yes. You are correct. You will only need to configure the ports with hosts connected (Servers/PCs etc..) as edge ports and not the trunk links between switches.
    Please let us know if you have any other questions.
    Thank you.

    Best regards,
    Andrew


  • 5.  RE: STP topology changes

    Posted 08-10-2017 23:06
    Thanks for this, out of interest is there any benefit to adding a designated root bridge? I disabled STP in our env for now and a ton of network issues have disappeared so I need to get it right when I re-enable it.


  • 6.  RE: STP topology changes

    Posted 08-14-2017 10:49
    Right, so I only need to enable edge-ports on the ports workstations are plugged into and not inter-switch trunks ?


  • 7.  RE: STP topology changes

    Posted 08-14-2017 21:23
    Thanks Andrew, also any reason to specify a designated root bridge?


  • 8.  RE: STP topology changes

    Posted 08-14-2017 21:23
    You should always specify a root bridge, otherwise the system will determine a root bridge based off of MAC address and that can be unpredictable. all your nodes will block or forward based upon path to that root bridge, so usually it is place pretty centrally in the environment.