How to remove an interface from spanning tree?

Discussion in 'Cisco' started by Hoffa, Jun 18, 2007.

  1. Hoffa

    Hoffa Guest

    Hello folks

    We have a triangle shaped L2 network with three 6513 switches and
    spanning tree enabled on all vlans to handle loop configuration.
    Pretty basic I guess. Today the fiber link between our root 6513 and
    the "secondary" 6513 went down due to supplier error, but everythings
    OK using the other links previously blocked by STP and I disabled the
    interfaces on the broken link not to confuse STP if the link comes up.
    Now our supplier tells us to start testing the link but I don't want
    to risk STP sync during office hours. Is there a way to bring up an L2
    interface without participating in STP negotiation?

    Regards
    Fredrik Hofgren
     
    Hoffa, Jun 18, 2007
    #1
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  2. Hoffa

    Trendkill Guest

    On Jun 18, 3:49 am, Hoffa <> wrote:
    > Hello folks
    >
    > We have a triangle shaped L2 network with three 6513 switches and
    > spanning tree enabled on all vlans to handle loop configuration.
    > Pretty basic I guess. Today the fiber link between our root 6513 and
    > the "secondary" 6513 went down due to supplier error, but everythings
    > OK using the other links previously blocked by STP and I disabled the
    > interfaces on the broken link not to confuse STP if the link comes up.
    > Now our supplier tells us to start testing the link but I don't want
    > to risk STP sync during office hours. Is there a way to bring up an L2
    > interface without participating in STP negotiation?
    >
    > Regards
    > Fredrik Hofgren


    Remove the fiber, remove the trunk config, put it as an access port in
    a non-intrusive VLAN, and don't put the trunk back-on till you have
    scheduled a proper outage.
     
    Trendkill, Jun 18, 2007
    #2
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  3. Hoffa

    Trendkill Guest

    On Jun 18, 3:49 am, Hoffa <> wrote:
    > Hello folks
    >
    > We have a triangle shaped L2 network with three 6513 switches and
    > spanning tree enabled on all vlans to handle loop configuration.
    > Pretty basic I guess. Today the fiber link between our root 6513 and
    > the "secondary" 6513 went down due to supplier error, but everythings
    > OK using the other links previously blocked by STP and I disabled the
    > interfaces on the broken link not to confuse STP if the link comes up.
    > Now our supplier tells us to start testing the link but I don't want
    > to risk STP sync during office hours. Is there a way to bring up an L2
    > interface without participating in STP negotiation?
    >
    > Regards
    > Fredrik Hofgren


    Oh, and plug back in the fiber after the trunk is removed, that way it
    will come up physically, but will not run spanning-tree accept as an
    access port and only in that VLAN.
     
    Trendkill, Jun 18, 2007
    #3
  4. Hoffa

    Scott Perry Guest

    QUICK ANSWER:

    interface FastEthernet X/X
    spanning-tree portfast bpdufilter enable
    switchport access vlan X

    Reference (website and links):
    * www.cisco.com
    * Support
    * Documentation
    * LAN Switching
    * Spanning Tree Protocol
    * Design TechNotes
    * Spanning Tree PortFast BPDU Guard Enhancement
    Look into the section regarding BPDU Filter

    This feature of BPDU guard disables sending and receiving of bridge protocol
    data units which are the basis for sending and receiving spanning-tree
    protocol information between ethernet switches.

    RECOMMENDATION:

    Don't do it! You have three switches which are in a loop. The loop is
    currently broken by disconnecting the trunk between the primary and
    secondary switch. You want to re-establish the loop by connecting the
    primary and the secondary switch back but remove spanning-tree from the
    interface. This risks creating a loop because spanning-tree information to
    prevent the loop will not be passed between switches.

    I say keep the interface between the primary and secondary switch in a
    shutdown state until you are ready to move the spanning-tree root role from
    the secondary switch back to the primary. If you want to bring up the
    connection earier, change the primary switch spanning-tree priority (which
    is not the root at this time) to a lower spanning-tree priority for all
    VLANs. Bring up the link normally, probably as a trunk if that is what it
    was, and change your spanning-tree priority back to normal values after
    hours.

    Referenced Cisco command line warning:
    Warning:ports enabled with bpdu filter will not send BPDUs and drop all
    received BPDUs. You may cause loops in the bridged network if you misuse
    this feature.
    ===========
    Scott Perry
    ===========
    Indianapolis, Indiana
    ________________________________________

    "Hoffa" <> wrote in message
    news:...
    > Hello folks
    >
    > We have a triangle shaped L2 network with three 6513 switches and
    > spanning tree enabled on all vlans to handle loop configuration.
    > Pretty basic I guess. Today the fiber link between our root 6513 and
    > the "secondary" 6513 went down due to supplier error, but everythings
    > OK using the other links previously blocked by STP and I disabled the
    > interfaces on the broken link not to confuse STP if the link comes up.
    > Now our supplier tells us to start testing the link but I don't want
    > to risk STP sync during office hours. Is there a way to bring up an L2
    > interface without participating in STP negotiation?
    >
    > Regards
    > Fredrik Hofgren
    >
     
    Scott Perry, Jun 18, 2007
    #4
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