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S8T8
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Spanning Tree on Access Point

Sun Aug 06, 2023 3:52 am

Hello, it should and easy question;
in a basic topology, Router -> Switch -> AP is RSTP useful/necessary? Or protocol=none is OK?
Is the use of CAPsMAN making any difference?

WiFiWave2 wiki says
If the CAP is hAP ax2 or hAP ax3, it is strongly recommended to enable RSTP in the bridge configuration, on the CAP...
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holvoetn
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Re: Spanning Tree on Access Point

Sun Aug 06, 2023 9:12 am

If you are CERTAIN there will NEVER be loops in your setup, xSTP is not needed.
That's how I understood it.

But can you be sure all the time ?
 
S8T8
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Re: Spanning Tree on Access Point

Sun Aug 06, 2023 4:17 pm

You're saying better have it than don't?

Loops happens plugging more than one ethernet cable, right?
 
holvoetn
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Re: Spanning Tree on Access Point

Sun Aug 06, 2023 4:20 pm

Or wifi bridges or router to switch to router to other switch to router, ...
 
kravemir
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Re: Spanning Tree on Access Point

Mon Dec 04, 2023 8:35 am

This doesn't make sense.

The recommendation to use RSTP does refer to use of hAP ax2 or hAP ax3 as CAP. But, it doesn't refer to use of any switches or existence of L2 loops in the ethernet topology.

If there are L2 loops in ethernet topology, then RSTP would be recommended regardless whether CAPsMAN/CAP functionally is being used for wireless interfaces. Which makes it orthogonal topic.

The CAPsMAN/CAP example in the docs isn't for meshing either. Which could result in L2 loops. And, there are different protocols for that.

So, only a rogue device, or heavily misconfigured/misbehaving device, could connect to multiple access points and bridge them. Which shouldn't happen normally either.

Wireless ports are practically edge ports then. And, they should become edge ports automatically according to bridge docs:

auto - same as no-discover, but will additionally detect if a bridge port is a Wireless interface with disabled bridge-mode, such interface will be automatically set as an edge port without discovery.

So, is this not working properly? Could it be causing issues, when wireless interface comes from inactive state to active - when first device connects to it - after long inactivity?

If so, then maybe setting bridge ports as edge (yes, or yes-discover) would work? I am using CAPsMAN static interface provisioning anyway - for VLAN capability on 802.11ac devices.

Though, dynamic interface provisioning probably doesn't allow to set port as edge manually, and use of RSTP is a mitigation of the some deeper issue with wireless drivers?
 
S8T8
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Re: Spanning Tree on Access Point

Mon Dec 04, 2023 11:48 am

@kravemir I'm not that expert for a proper answer, about xSTP the answer received from support was that protocol-mode=none is fine but not for AX devices with switch chip not enabled for hardware offloading.
 
whatever
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Re: Spanning Tree on Access Point

Mon Dec 04, 2023 2:51 pm

From my experience the automatic edge port setting on wifi interfaces does not work and will cause roaming issues when (R)STP is enabled.
I have therefore disabled any kind of spanning tree on hap ac2 as well as hap ax2 and so far have not noticed any issues caused by this on either of them. Why would a bridge without any kind of hardware offloading require RSTP enabled? Maybe there is some kind of hidden bug in ax devices that can be worked around by RSTP?

Edit: https://help.mikrotik.com/docs/display/ ... Offloading says that hw acceleration on IPQ-PPE switch chip is still "work in progress". Maybe they are just suggesting to enable RSTP to ensure HW acceleration remains disabled? I have vlan-filtering enabled on my hap ax2, so HW acceleration is disabled anyway.
 
S8T8
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Re: Spanning Tree on Access Point

Mon Dec 04, 2023 3:27 pm

Nothing mysterious, as you noticed in Bridge Hardware Offloading
Currently, HW offloaded bridge support for the IPQ-PPE switch chip is still a work in progress. We recommend using, the default, non-HW offloaded bridge (enabled RSTP).
Any condition that disables HW offload is fine on switch chip IPQ-PPE (mostly AX devices).

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