ArubaOS and Controllers

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Occasional Contributor I
Posts: 9
Registered: ‎07-21-2009

Controller and Spanning tree

Does Aruba controllers support splitting the controller connections between two switches?

We configured an MC-3200 and had 2 links going to 2 separate switches and the switches are trunked. After enabling the controller links CPU spiked up to 100% on both switches.

thanks!
Guru Elite
Posts: 20,819
Registered: ‎03-29-2007

Per Vlan Spanning Tree

Alng1,

Aruba controllers do NOT support Per-Vlan Spanning Tree. One solution is to turn off spanning tree globally on Aruba Controller and allow your own infrastructure to manage/moderate spanning tree.


Colin Joseph
Aruba Customer Engineering

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Occasional Contributor II
Posts: 100
Registered: ‎11-07-2008

Re: Controller and Spanning tree

Alng1 - We have spanning tree dual linked on our controllers and it works great. It took a little configuring to get it working though. What core switches are you using? We are using Cisco 3750's for the wireless core. The config is definitely not a normal spanning tree config like you would expect to see, but it works 100% of the time.
Aruba Employee
Posts: 509
Registered: ‎07-03-2008

Re: Controller and Spanning tree

Alex - Be careful not to have portfast enabled on the switch ports that the controller interfaces are connected to. You will almost certainly cause a loop, even if it's temporary. Considering your switches hit 100% CPU, it looks like you did cause a loop.

FYI, Aruba's recommendation on spanning-tree is to disable it on any controller if there is PVST running in the distribution layer of the LAN.
Occasional Contributor II
Posts: 17
Registered: ‎05-29-2009

Re: Controller and Spanning tree





Hi gwilliams, Would you mind to share your 3750 spanning tree configuration? I am thinking to dual home the controllers but since we have rapid-pvst in our switch it always give me problem when connect as redundancy.

Thanks,

SL

don
Contributor I
Posts: 31
Registered: ‎04-03-2007

Re: Controller and Spanning tree

Are you sure Aruba's reccomendation is to turn off STP when connected to PVST (Cisco) switches? Rapid Spanning Tree is supported (or at least documented) in 3.4. I tested this briefly with one of my M3's and a Cisco 3750 and did not see the CPU issue described here, Can someone offer more information on this and actual usage experience?
Guru Elite
Posts: 20,819
Registered: ‎03-29-2007

Rapid Spanning Tree

Rapid Spanning tree is supported in 3.4.1 and above, but PER-VLAN spanning tree is not. That is why you turn it off on the Aruba side and have Cisco manage per-VLAN spanning tree. If you leave spanning tree enabled on the Aruba controller, the Cisco switch will see the same bpdus, and shut down one port of a dual-connected controller, even if both ports are on different vlans.

In Optimizing Aruba WLANs for Roaming Devices v.3.3 here: http://www.arubanetworks.com/pdf/technology/DG_Roaming.pdf it mentions to "Disable spanning-tree in order to not conflict with the uplink distribution switches that usually have the standard spanning-tree or other versions of this protocol enabled in order to provide sufficient redundancy."


Colin Joseph
Aruba Customer Engineering

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Occasional Contributor II
Posts: 100
Registered: ‎11-07-2008

Re: Controller and Spanning tree

Maybe things have changed, but when we tried just spanning tree through Cisco it didn't work.

Here is what you need to have on your 3750's

spanning-tree mode pvst
spanning-tree loopguard default
spanning-tree logging
spanning-tree portfast bpduguard default
spanning-tree portfast bpdufilter default
spanning-tree extend system-id
spanning-tree vlan x,xx,xxx-xxx priority 24576

For each trunk port on the 3750's
spanning-tree cost 1000

And on the aruba's themselves:
spanning-tree priority 65535

For each uplink port on the aruba controllers:
spanning-tree cost 1000


This is the only way we were able to get it to work 100%. We worked with a CCIE at Aruba to get this to work. It is not a standard Cisco configuration. We tested with multiple Cisco switches, not just the 3750's, and had the same result. You would think that turning off spanning tree on aruba's and letting the cisco's handle it would have worked, but it doesn't. We are running 3.4.1.1

Just to make sure we are on the same page, here is our configuration. 10 controllers, each in a separate building, each dual linked fiber to 2 separate 3750's in 2 separate buildings via fiber.
don
Contributor I
Posts: 31
Registered: ‎04-03-2007

Re: Controller and Spanning tree

To Mike's point, the Aruba controllers only run one spanning-tree instance and if your vlan lists are different on each uplink, this won't work for you. In my case, I am only looking for failover to my two cisco core switches and my vlan lists match on each side. You also have to make sure the native (untagged) vlan matchs between the cisco and Aruba sides of the trunk as this is where all the tag information is passed.
My testing with RST worked for this purpose (3.4.0.1) but I will re-test and post complete results after we upgrade in a few weeks.
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