carp demotion triggered by send error 55

[ctr]

I'm using a opnsense 19.7 HA cluster on two identical ESXi systems. Everything runs fine (after the initial virtual switch configuration) generally. However after a few weeks I randomly get "kernel: carp: demoted by 240 to 240 (send error 55 on vmx0_vlan41)"

If found two reference, but both don't have a resolution:
https://forum.netgate.com/topic/78354/send-error-55-with-vtnet
https://forum.opnsense.org/index.php?topic=5476.0

Does "send error 55" really point to "No buffer space available" (as defined in sys/errno.h) and what could it mean in an opnsense installation?

[mimugmail]

If you have send_error you can set the tunable to 0. Normally this doesn't disturb your cluster. Just google for tunable OPNsense send_err carp :)

[ctr]

Yes, I already set it to 10 because the error is so seldom I may get away with it. However, at the same time I was wondering what the root cause is (as using tunables is only the last resort).

[mimugmail]

I never experienced it myself, maybe some combination of nic, driver and spanning-tree?