Weird MTU Issues

[Adam.P]

I have a very basic LAN/WAN configuration with static WAN address and a few ipsec vpn connections. I started investigating this one location because of poor VPN performance.

I did the "old ping MTU test" and found some interesting results that I'm not able to replicate anywhere else.

If I run this command while behind my opnsense: ping 8.8.8.8 -f -l 1473
I get the following: "Packet needs to be fragmented but DF set."

If I run this command while behind my opnsense: ping 8.8.8.8 -f -l 1472
I get the following: "Request timed out."

I don't begin to get replies until I get to: ping 8.8.8.8 -f -l 512
512 bytes and below reply.

I've put a laptop in place of my opnsense appliance with the static IP and it works as expected. Packets under 1473 bytes all reply. Can anyone shed some light on this? I'm running version 19.1.4.

Thanks!

[Adam.P]

Someone? Anyone?