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?
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.
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.
* 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 ________________________________________
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