I have a problem with spanning tree and ports being disabled. I don't know what to do and it is annoying me at times and prevents me from working. Maybe someone has an idea for further debugging.
My client (macOS) is directly connected to a FortiSwitch (124E), which in turn is directly connected to my 40F (trunk). There are some VLAN configured. Occasionally, the port (port20) my client is on gets disabled every few seconds and I lose connectivity.
FortiOS is on 7.0.8 and FortiSwitch 7.0.5. The network setup is very simple.
primary switch port port20 has gone down
primary port port20 instance 0 changed role from designated to disabled
primary port port20 instance 0 changed state from forwarding to discarding
primary switch port port20 has come up
primary port port20 instance 0 changed role from disabled to designated
What I have tried so far:
Various FortiSwitch port settings (STP, BPDU Guard, Root & Loop Guard, disable, etc.).
Disabling the trunk to the FortiGate (connectivity only via one link).
set the speed settings to "1Gbits only" or "auto
disable the WLAN interface (Ethernet only) on the client
firmware upgrades (FTG and switch)
The error also occurred with other firmware. On the client there is a desktop hypervisor (Fusion) and one VM in bridge mode, but it is disabled. I am not sure if this could have an impact but it does not fit together in time
Hi Albert, I did the remote session with Fortinet support. The problem appears to be an incompatibility between RSTP and MSTP. The FortiSwitches only support MSTP which is backwards compatible with RSTP, but apparently it's not talking properly with RSTP (in my case these are Alcatel-Lucent switches). So MSTP goes through all spanning-tree phases cyclically, that's why I see logs of STP status continuously. To resolve it, MSTP must also be configured on the switches in cascade to FortiSwitch.
Were you able to resolve this? I don't have Alcatel-Lucent switches, I have a full FortiStack, with one Cisco 2960.
HA Pair of 200F
2 x 1048E setup with an MC-Lag ICL between them
7 x 548D, each wired to both 1048E
1 x 108E hanging off a single port of a 548D
What caused us to notice the issue is the uplink to the newly added 108E keeps going into a blocking status, with log entries very similar to the ones posted by the OP. While researching this, I noticed uplinks between the 1048E and 548D are going into blocking too, but with everything redundantly cabled, the users aren't feeling the impact.
We do have one Cisco 2960s hanging off a single port of the 1048E, perhaps this Cisco is injecting some weirdness into MSTP?
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