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Hoffa 06-18-2007 07:49 AM

How to remove an interface from spanning tree?
 
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


Trendkill 06-18-2007 11:04 AM

Re: How to remove an interface from spanning tree?
 
On Jun 18, 3:49 am, Hoffa <fredrik.hofg...@gmail.com> 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 06-18-2007 11:05 AM

Re: How to remove an interface from spanning tree?
 
On Jun 18, 3:49 am, Hoffa <fredrik.hofg...@gmail.com> 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.


Scott Perry 06-18-2007 05:48 PM

Re: How to remove an interface from spanning tree?
 
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" <fredrik.hofgren@gmail.com> wrote in message
news:1182152999.046379.130560@c77g2000hse.googlegr oups.com...
> 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
>





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