On my 27” 2020 iMac why is the custom MTU setting in Mac OS Sonoma 14.0 max only 1436 and not the standard 1500 ? After testing in terminal my best MTU should be set at 1480. But I can’t customize it above 1436. On my older iMac it has a MTU custom setting max of 1500.
iPhone 8
dialabrain wrote:
MrHoffman, is there any benefit to changing the MTU from the default 1500? All my Macs are set to 1500 and I've never had any issues. I know zip about networks.
I configure jumbo frames on various enterprise networks, roughly 9000 bytes, depending.
This requires some care to ensure that all devices (NICs, routers, switches) in the network path involved can support that.
Bigger packets means more data can be transmitted between the inter-packet gaps, which usually means higher bandwidth and lower latency.
But for most folks and most applications, the default MTU ~1500 works just fine, and avoids learning more about IP and routing, and learning which NICs and which switches are… problematic. Chasing connection errors in complex networks due to MTU sizing issues is less than fun. (This is where a ping sweep usually gets used, too.)
There are useful details and descriptions in this thread:
… https://discussions.apple.com/thread/253016338
For what MTU a particular network—cellular or otherwise—supports, check (sweep) it, and check with the technical documentation and with technical support group.
Matti Haveri wrote:
AFAIR some VPN services might require MTU less than 1500. Years ago I once had to do that because otherwise the connection was very slow with intermittent data bursts (an old Cisco VPN to work).
VPNs are built upon IP routing—VPNs are effectively IP routers with an intervening encrypted link—and packets traversing IP routers fundamentally involve the MTU configuration and limits.
Here is how to size the MTU, if you don;t want to use the automatic sizing:
Confirm your current network configuration supports the particular MTU size you want to use.
Dialabrain I am setting the MTU right where you photo shows under sytem settings, network, wifi, details and hardware to MTU. As you can see in my photo. On Sonoma if you click manually and go to custom you can only type in between 1,280 to 1,436. If you type in a higher number it automatically diverts back to 1,436 after you close it.
Appears that way. I wish Apple would explain why ?? I have an older iMac running on an older OS. In the preferences on it I can chose a custom range up to 1500. So I am able to set my MTU at 1480 for my best internet speed (after figuring it out in terminal).
Where are you trying to change it?
MrHoffman, is there any benefit to changing the MTU from the default 1500? All my Macs are set to 1500 and I've never had any issues. I know zip about networks.
I tried but like in my recent photo I am unable to go above 1,436. I must be between 1,280 to 1,436.
You seem to have Configure set to Automatically. Mine is set to Manually. That may be the difference. As you may notice in my post to MrHoffman, I know next to nothing about networks.
FWIW, if I change to Custom, I have the same range you show.
MrHoffman wrote:
But for most folks and most applications, the default MTU ~1500 works just fine…
+1 Thanks. So for home/personal use, there's really no reason to switch from the default 1500.
Smudgie-Cat wrote:
Appears that way. I wish Apple would explain why ??
Apple rarely if ever explains the technical reasons for changes.
So from what it seems, Custom settings are limited to 1,280 to 1,436. apparently a limit imposed by Apple.
AFAIR some VPN services might require MTU less than 1500. Years ago I once had to do that because otherwise the connection was very slow with intermittent data bursts (an old Cisco VPN to work).
OS Sonoma Custom MTU setting
