XS716T and Jumbo Frame MTU

[WebsterWebster]

I actually have an XS716T but that model didn't appear in the drop-down list or models.

I am looking at Configuring jumbo frames on NETGEAR ProSAFE switches . It shows to set a jumbo frame MTU size of 9216. When I try to set that value on my XS716T with firmware 6.6.3.3, I get an error popup that says 9216 is out of range and the valid values are from 1500 to 9198.MTU size errorI 

I assume I need to use 9198 as my MTU value for jumbo frames?

If the instructions say to use 9216, why is 9216 an invalid value?

Why is my model XS716T not in the drop-down list?

XS716T

Thanks

Webster

[schumaku]

The maximum frame size depends on the switch design and SoC in place. The XS708T, XS716T, XS728T, XS748T Data Sheet does (somewhat lazy) talk of Jumbo frame support "Up to 9K packet size" for the XS708T and the XS716T, and "Up to 10K packet size" for the XS728T and the XS748T (which don't have an ability to configure the max frame size per port).

The 9216 example (as shown on a top of the line witch with 12k frame support) is - while common - kind of a randomly chosen number to include whatever padding and the like.

@bradleyv or @LaurentMa can you shed some light about the slightly uncommon smaller 9198 here? An exact number on the data shet would make things clear, too.

[WebsterWebster]

Should the 1G ports also have extra padding for frame headers? The original article I linked shows the 1G ports with an MTU of 1518.

Thanks

Webster

[schumaku]

While the XS716T has no GbE ports, in general, a basic Ethernet frame does start with 14 Bytes of Ethernet header, can take max 1500 Bytes of payload, and has a trailing four Bytes CRC ... this makes up the 1518 Bytes. It can be four Bytes more if 802.1q VLANs are in the play, and much more...

Rergards,

-Kurt

[WebsterWebster]

I have no VLANs (and have no idea how to create or use one) so I should set the MTU to 1518 for the ports that will operate at 1G.

Thanks

[schumaku]

Please explain me why you want to limit the max frame size on any port. One day you might want to run Jumbo Frames between say Windows or macOS computers and a NAS/storage server/Windows Server what does create massive relief on the protocol overhead ... just as one example.

This problem is somewhere between academic and non-existing. Put all ports to the max allowed frame size. You won't experience any issues.

Should there be a problem with a connected device, a network link to wherever, you can still apply a limitation on that port.