Should I disable spannig tree on a wireless cotroller port and connect that to a core switch with Spanning tree?

Pkafkas used Ask the Experts™
How should spanning tree be designed?

I have a wireless controller that is essentially a switch and that is connected to a core switch.  The port, from the wireless controller is set with spanning tree turned on.  The core switch is using Spanning tree )(2 fiber connections on each switch uplink port.

I want to use another port on the same wireless controller that will be connecting to other switches.  Should I disable spanning tree on the other ports or not?  If these other ports on the wireless controller have spanning tree disabled will that cause any loop?

I have never worked with spanning tree before and I am not sure what I should do?  But I do not want to bring the network down.  Again Spanning tree I enabled on the core switch ports that will connect to the wireless controller.  Should I have spanning tree enabled on the wireless controller ports or will disabling spanning tree on the wireless controller bring the network down?

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if the other switches are connected to one another or the existing one, obviously on the same vlan/vlans, you do need spanning tree. otherwise you do not.

it is considered best practice to concentrate active spanning tree on a central equipment if possible and only let spanning tree packets through on others. this makes debugging easier and prevents spanning tree flappings.

my personal policy and recommendation is whenever possible, use redundant network settings that do not produce loops and do not require spanning tree. for example, you may want to stack your switches and use lacp between the switch stack and the wireless controller
PkafkasNetwork Engineer


On the Aruba controller will I need to enable spanning tree on port 0/0/1?  Right now, I have spanning tree disabled on port 0/0/1, pon the Aruba 7030.

It is currently set on port 0/0/7.  I am afraid of bringing the network down.  It might be important to mention that after I disabled spanning tree on the test Aruba controller the test HP Switch never went down.

I have never worked with spanning tree before so I can not sure what to expect.
given the provided schema, there is no loop in the network design. that would mean spanning tree is useless, but the schema may also be incomplete.

spanning tree basically has 2 modes of operation with different names depending on the vendors.

an active spanning tree node will send specially crafted packets on the network. if one of these packets loops back through a different port, the switch will assume there is a loop and bring the port down. such packets usually flow about once per second.

a passive spanning tree node will let said packets flow through it

spanning tree can either work per port or per vlan. using multiple links with different vlans and port based spanning tree at the same time is asking for trouble. maybe this is what happened in your case.

based on the above i'd assume you don't need spanning tree

if multiple ports in the same vlan are connected between the controller and the switch, you should rather configure LACP nic teaming

if the connected ports are in different vlans, there is no reason why spanning tree would be needed

basically you need spanning tree when you connect multiple switches in a ring. in other cases, loops indicate some misconfiguration that should be corrected rather than automagically detected by the switch
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PkafkasNetwork Engineer


The Aruba controller 0/0/7 trunked with multiple tagged vLans and 1 Native VLan.  The matching configuration is to the ethernet ports on the Core Swtich(where the Aruba 7030 is connected to).

IS it safe to understand spanning tree is not required on the Aruba Controller 7030?  I guess the test will be to try it out.
if spanning is indeed required, the whole network will be heavily impacted within seconds so you'll notice, assuming at least a few packets are sent.

a very efficient test tool is a ping flood. if there is a loop, the network will die and stay dead after you stop flooding and until you unplug one of the cables.

i'm unsure i get the exact topology so i'd rather not state whether there is a loop but from what i gather, the answer would be no.
thanks. feel free to request some follow up help should you need any
PkafkasNetwork Engineer


It was decided that since the Aruba 7005 had STP enabled and connected directly to the HP Test Lab Switch (STP not enabled)...

But the HP Test Lab switch was also directly connected to the Core Switch (STP Enabled)... that was what caused the Test LAB switch to go off line.  2 separate connections to 2 separate switches that had STP enabled and they confused the Test LAB switch thinking a loop was in place and took it off-line.

I have a lot to learn about spanning tree; but, it appears that it is best practice to enable STP on the core switch and not the edge switches.  If you are in a situation that an edge switch will connect to 2 differetn devices with STP enabled then that will bring down the edge switch's connection to the network.
I have a lot to learn about spanning tree; but, it appears that it is best practice to enable STP on the core switch and not the edge switches.

yes. centralize spanning tree if possible and make sure spanning tree packets are allowed to flow through other equipment. in the situation you describe above, it is actually one of the equipment with spanning tree enabled that will bring the port facing the switch down. typical scenarios also include flapping between level 2 paths which usually ends up producing 1/4 ping failure. those would occur when you actually do have a loop and multiple active spanning tree equipment in the loop.

nb : it is best practice to disable spanning tree entirely if you have no loop in your topology.

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