To xSTP...or not

RouterOS General
1

I red a lot about using Spanning Tree Protocol and found that it is recommended to use RSTP when using hAP ax2 and hAP ax3.


If the CAP is hAP ax2 or hAP ax3, it is strongly recommended to enable RSTP in the bridge configuration, on the CAP

configuration.manager should only be set on the CAP device itself, don’t pass it to the CAP or configuration profile that you provision.

I’m running a network which is shown in the image below, and am using a total of 5 VLAN’s.

My question, should I enable xSTP? And should it be MSTP due to the different VLAN’s? Or RSTP? Or can I leave it to None?
For your information, all CAP’s, controlled by the RB4011, are using the new wifi-qcom-ac driver.

2

The short answer is “unless you really have something against it, it costs nothing to enable it.” I would make the case that in a Mikrotik environment, it is actually better to have something rather than “none”: during a recent troubleshooting (LLDP), someone pointed that protocol “none” means that all L2 broadcast/multicast are sent on all ports. This includes STP, LLDP, CDP, plus a few proprietary protocols. Quite noisy.

Now, STP, RSTP or MSTP - STP is older and slower, out of the picture. If you don’t need to complexity of multiple spanning-tree instances, for example you don’t need to have different roots for different VLAN groups, then RSTP is your best friend: it is quite fast and converges quickly.

Regardless of which STP flavour:

  • Set the bridge priorities! Your RB4011 seems a good candidate to have a prio of 0 and be the root, with the hex Poe connecting to the powerbox having a prio of 4096 to be the backup root.
  • Define the edge ports. That will speed up things quite a bit.

My 2 cents.

3

As long as you’re sure there won’t be any (physical) loops in your network, then you can set anything between none and mstp. However, if you foresee loops (could even be they are there by LAN design), then you need some varuant of STP. If you want to have physical loops but from VLAN topology point of view there are no loops, then you need MSTP. If VLAN topology follows physical topology (i.e. redundant links are active or disabled for all VLANs at the same time), then RSTP should suffice.

4

Thanks all, did learn something thanks to you.
I chose RSTP and set priority. Still not sure what edge ports (though I can think of something) are and what can be changed in my config.

As the network won’t be (more) complicated then it is currently, I’ll keep RSTP active.

5

Hi @erlinden, it’s an interesting topic and I want to share some researches;

I have a very basic topology, Router → Switch → APs,
Router and Switch are connected via Trunk ports trough DAC 10G and Ethernet 1G (disabled, at the moment).

From: https://help.mikrotik.com/docs/display/ROS/Bridging+and+Switching#BridgingandSwitching-BridgeHardwareOffloading

If the CAP is hAP ax2 or hAP ax3, it is strongly recommended to enable RSTP in the bridge configuration, on the CAP...

Guntis answered in a ticket:

Regarding hAP ax2, hAP ax3 we recommend enabling RSTP on the bridge because it turns off 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).

basically you need xSTP enabled to avoid any issue, if you use vlan-filtering=yes you’re safe to disable it.

You can find some answers in my topic: http://forum.mikrotik.com/t/how-to-show-all-ssids-from-device-on-its-label/18623/3
In my case I don’t need xSTP, until backup ports are enabled.

Respectable engineer @StubArea51 a.k.a. Kevin Myers wrote on Reddit:

MSTP is more interoperable with other vendors and doesn’t have issues with STP diameter the way RSTP does. It’s the best version of STP imo even if you aren’t trying to map different forwarding topologies on VLANs.

I always use MSTP by default

then in another ticket Edgars from support wrote:

Changing STP versions (from MSTP) does not make any difference to the packet forwarding performance.

Also, just enabling MSTP without configuring MSTIs does not make any improvement over the RSTP.

At the moment I left MSTP enabled, trying to figure out how Edge and Point-to-Point works, (if you need I can share more info about it), for a basic use as @mkx wrote RSTP is enough, you can noticed that MSTP is more present in changelog / issues, due to be more complicated it can create issues in future.

Hope this helps.