Home Lan 9k MTU on 10G vs. internet out on 1500

Hi Experts.

What is a good approach to set up MTUs for a home lan that runs 10G fiber on Ubiquity gear, then goes into a NetGear SG3100 and then into a ISP router and from there its the ISPs internet?
I gather when one pings with -f -l 1472 you see 0% loss (assuming the switches are on 1500).
What do I set to get max speed on my 10g lines form the clients to the switches (I’ve tried 9k)
What do I set in the ubiquity switches (I’ve switched jumbo frames on)
What do I set on the LAN side of the PFsense (if that is possible)
What do I set between the WAN side of the PFSense to the ISP router?

Hey, rondv5 -

I’m definitely no expert in home LANs, so there’s probably going to be more relevant answers than mine in your future. I’m mostly here because you mentioned MTU.

My approach to MTU (and really, life in general) is to only add necessary complication. If the type of traffic that you’re pushing through the network does well with large MTUs - like stuffing huge video files through from host to host - then rock on! But you should be in control of the frame size setting of every device in the path and you will need to remember to set them all, and troubleshoot them when the lack of standardization between disparate manufacturers gives you one of those fun “intermittent” projects to work on. And all of this to save some overhead.

Granted, it’s not insignificant, but overhead rarely tips the scales for me, especially in a small LAN with a data firehose. It’s not insignificant, but usually something like 10g (assuming zoomy hosts that can process data along with that Autobahn network) makes it fairly irrelevant. Main exception being fairly busy storage networks, and I never expose those to a router, much less a firewall. In rare cases not even a switch. :smiley:

That being said, it is fun to see your monster MTU reported in testing.

Even if your ISP is also with you on this jumbo frame journey, your jumbos are going to fragment somewhere in the intertubes (or worse, be dropped by some routers) so I wouldn’t worry about your firewall’s WAN interface. You’re going to have plenty to deal with inside.

For the rest I’d spend some quality time with iPerf, Wireshark, your favorite focus music and some sort of beverage that helps you methodically work your way through testing payloads through your network.

Happy hunting!