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STP Issues with HP Switches: 1920-24G (core) 1810-8G (satellite)

  • 8 March 2018
  • 6 replies
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I have a HP 1920-24G as core switch and am adding a HP 1810-8G to replace an unmanaged switch in a media room.

The 1920 has 4 ZPs directly wired to it. The 1810 is at the end of a drop from the 1920. On the 1810, I have a Connect attached, which also has a line in from the media amplifier. The Connect also provides sonosnet connectivity to a pair of Play 3's and one Play 5 that are too far from the switch/ZP area.

To get the setup working, I disabled wifi (sonosnet) on the 4 wired ZPs and enabled STP on the 1920 and on the 1810. I set the priority of the 1920 at 4096 and the priority of the 1810 as 8128. The system is operable (no diabling broadcast storms), but the Connect is showing up as root on the Sonos STP, not the HP 1920. My understanding is that the MAC of the 1920 should be the system root. In the 1920 diagnostic file and on the 1810 configuration page, it appears that the 1920 is root - it's just in the Sonos STP output that the 1920 is not root.

In screenshots below, 40b9-3c8f-929f is MAC of the 1920.

SONOS STP CONFIG



SONOS MATRIX



HP 1920 - Partial configuration - Global Settings and Port 22 - drop cable to 1810 switch



HP 1810 - STP Configuration

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Best answer by jishi 8 March 2018, 13:41

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6 replies

Could you perhaps have multiple spanning trees active?
Userlevel 1
Your HP switches are running Rapid Spanning-tree 802.1w as per the screenshots and I believe Sonos runs STP (802.1d), It is configurable on the HP switches... you could try it if possible...
Userlevel 4
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Not sure what root port and root path cost affects the election of root bridge, but that might have something to do with it.

I advice you to adjust the path costs for the switches, since they are running RSTP. Either, run them in classic STP, or set the path cost for each port according to classic standard (RSTP have some advantages over classic that you may or may not care about). I have successfully managed to get a managed switch as the root bridge for a Sonos system, but the reporting from the STP page was inconclusive (https://en.community.sonos.com/troubleshooting-228999/only-tertriary-nodes-how-is-it-possible-30888). This was a long time ago though, and I don't remember exactly what I did.

But baseline, path cost needs to be correct for any port that has Sonos gear connected, and also for the link between the switches (any switches that has Sonos gear connected). If you do that correctly, turning on/off wifi has no relevance for the performance of your system. This is probably something that you should try to fix first.
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Thanks for the replies. The reason I used RSTP was that I had read in the HP manual and in several other posts/forums that the RSTP would default down on ports with devices using STP-legacy, but as you point out the logs don't show that to be the case.

So, I've been able to test some of this remotely, but will have to finish when I'm home tonight in case it set of a broadcast storm and shuts down internet at home while wife is there alone!

I have set the 1920 'core' switch to STP mode and path cost using 802.1d, which did assign 'legacy' path costs to those ports. 🙂 On the remote 1810 switch, setting to STP/802.1d does not correctly set the path costs, they remain at 802.1w values, so I'll have to manually change the path costs. :?

On this post (https://sonos.custhelp.com/app/answers/detail/a_id/2129/~/sonos-stp-switch-settings) and others, I have seen that the cost for ports with sonos devices should be set to 10 (not 19, which is standard for 100Mbs) - do you have any input on this approach?

Also, on the port on my core 1920 switch that connects to the 1810, it's a 1Gb connection, so I would imagine that keeping it at 4 is correct?

ratty - I'm not sure how to test whether there are multiple trees. My understanding is that only should occur under MSTP and only if you set up regions - but I am hardly an expert.
Userlevel 4
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10 or 19 shouldn't matter, the total cost just needs to be lower than what the wireless links would be set at. It varies depending on signal strength, but they are usually between 150-300.

And yes, setting the gigabit links to 4 seems like a good choice. Not that it matter much if you only have two switches and no redundant paths 🙂
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Thanks - this seems to have fixed the issue, as the sonos stp is showing the MAC of core switch as root. Also, the Matrix lists the wired devices as secondary nodes and the wireless devices as tertiary nodes - none are root. Further, setting the port from core to secondary switch to 4 and the sonos ports to 10 (or 19) seems to have the sonos units all working as I would expect: the connect looks like it is getting signal from cable and the 3 wireless speakers on far side of home are getting wireless signal from connect. None of the wired ZPs are forwarding signal to Connect or the far speakers.