I own a OpenWRT router with a rather complex configuration (VLANs, IPv6 tunnels, VPNs, ...). Everything works perfectly most of the time, but I am experiencing intermittent problems, that I suspect are related to wrong MTUs on some interfaces. I know about the "MMS Clamping" / "mtu_fix" options, but I have not found clear information on how and when to use them, or how to debug issues related to MTUs.
Does anybody have a link on information about this subject, please?
Many thanks!