Hello,

We have a total of 12 Omada Switches and for resiliency they are connected with redundant paths to 2 spline-switches (SX3016F)
Redunant paths are usually disabled using RSTP - but the Topology-Map seems to ignore that and concludes wrong topology for the whole network.

What exactly goes wrong could best be explained with the following buildings example:

- 3 x SG3452X
- Each of the units has a single fibre connection to one of the 2 splines located in the main building.
- To ensure connectivity, when either spline fails, all 3 units are connected with a 10G DAC-Cable as well.
- RSTP is doing it's job, and by properly setting path costs, the 3 fibre connections are active, the DAC-Connections are disabled.

However, what happens now:

1.) From the Switch H2_S1 (top one), the controller obtains the information, that there is the uplink to spline 1 (fine) and 2 downlinks to H2_S2 and H2_S3. (fine to some extend)
2.) For H2_S2, the controller is now falsly concluding, that the active uplink port (fibre to Spline 2) gotta be connected to H2_S1
3.) For H2_S3, the controller is now falsly concluding, that the active uplink port (fibre to Spline 1) gotta be connected to H2_S1 as well.

So, the topology algorithm seems to discard some information received from S2 and S3 and gives the reported downlinks of S1 precedence for generating the topology map, where S1 doesn't know that the downlink-paths are blocked by RSTP currently. I.e. the algorithm is taking a "shortcut" here, like: "If we already know there's a downlink from S1 to S2, then the active uplink of S2 only can be S1" - and that is not true for RSTP-Usage.

This error happens throughout the entire system, but this partial example makes it kinda obvious, what the algorithm is doing / ignoring I think.

ps.: the forums recaptcha doesn't show up in chrome. Just says "not verified", when attempting to post.