Network – MTU 9000 and 1500 when machines with MTU 1500 send data to machines with MTU 9000

linuxmtuNetworknetworking

we have some machines in the cluster

linux machines as Linux_a , linux_b are configured with MTU 1500

while linux machines – linux_1 and linux_2 are configured with MTU 9000

so

linux machines – linux_a and linux_b send heavy data to linux_1 and linux_2

is it a problem?

note – as I understand only scenario as:
send data from linux that configured with MTU 9000 to machine with MTU 1500 – is a problem

Best Answer

Generally, this should be avoided, but under some limited circumstances it may appear to work. The problem stems from there being no layer-2 mechanism to signal the mismatch, or negotiate a frame size.

However, so long as the larger MTU never sends anything larger than the smaller MTU, everything will appear to work. This will usually only happen if the smaller MTU is the only side to ever initiate a TCP connection; MSS will limit the size of frames from the larger side.

Note: I've done this in a few cases with iSCSI. As the server never opens connections, and only responds to client requests (that will never be larger than the client MTU), it will usually work. However, when two mismatched clients try to communicate -- eg. distributed filesystems, things can fall apart.

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