Maximum Transmission Unit

     Good evening. My computers Maximum Transmission Unit (MTU) is higher than the routers Maximum Transmission Unit limit. I have My computer is set to: 4,470 which is apparently the Fiber Optics Distributed Data Interface default requirement for High-Speed Serial Interfaces too. Can somebody reach an executive at NetGear? That seems unacceptable to not allow us to choose. My question is: Does that mean the Macs Maximum Transmission Unit although it's reading 4,470 on my computer doesn't actually go through? Since the router can't exceed 1,500?

Edited by supertopsecret, 19 December 2023 - 08:17 PM.

>> Can somebody reach an executive at NetGear? That seems unacceptable to not allow us to choose.

Since your router's Settings menu doesn't allow you to set the MTU over 1500, that's an obvious indicator that using a higher number will just screw up your router's functionality. Instead of trying to micromanage your router, just focus on configure it so it's secure and reliable.

https://routersecurity.org/index.php

If you do insist on messing up your own LAN however, avoid the default manufacturers firmware on your router and use a third-party option, like DD-WRT. Non-manufacturer firmware will often have a lot more options that are manually alterable.

https://www.maketecheasier.com/dd-wrt-vs-tomato-vs-openwrt-router-firmware/

You should only use higher MTU if you have complete control over the network from end to end.

Setting 4400 on your end and then your ISP sets it to 1500 will for sure mess up your communication. Dropped packets, or fragmentation having to be done or worse; you get some traffic through and some not.
Ive seen the weirdest things happen, like packets between 1472 and 1500 getting dropped while smaller packets went through just fine. Wrecked havoc on the VPN connection for sure and was a pain to figure out

Hth

tfn

 

As mentioned by @toofarnorth, Custom MTU settings can severely mess with your network if you do not have absolute control over the Transmission Unit settings on all transmitting devices. Your ISP will very likely use 1500 so any breakout traffic above that will get mangled.

To be clear, a higher MTU does not automatically mean faster transmission. Standard Ethernet Frame Payloads are 1500 Bytes long. They will not get longer unless all relevant devices are using Jumbo Frames.

If you are not specifically using Jumbo Frames there is no need to go higher that 1500.