My ATT fiber MTU says 1500. On the main device they give you when you setup with them.
When I ping on my home network where vpn is hosted:
ping 8.8.8.8 -f -l 1472
This is the highest it can go without fragmenting. 1472. I assume 28 for packet headers
I tested setting my MTU to 1472 in GLI.net router admin panel. When I did the ping test in terminal connected to my travel router:
ping 8.8.8.8 -f -l 1444
This was the highest it could go without fragmenting. I assume 28 for the wireGuard packet. wireGuard seems to take it out of the 1472?
So I thought, wouldn't I be able to set the MTU to 1500?
I did and now it pings on the travel router up to 1472. Just like on my home network.
What's the catch? that the network my travel router is on needs to be 1500? Is there high risk there of it not working well if my travel router is on different types of networks, like mobile carrier hotspots, or starlink, or idk.
My travel router was pinging from another fiber connection from the same ISP.. so probably the same MTU as my home fiber network... But isn't 1500 common for home ISPs?
In addition, I just tested the ping command on my mobile 5G phone and it looks like 1380 is the max it goes...
Wouldn't this mean the default wireGuard of 1420 be fragmenting if I was going through a mobile network on my travel router then? Shouldn't my MTU to set in Wireguard panel be 1408.. subtract 28 = 1380
if I ever plan to use my phone as a hotspot? Thanks.