Jumbo Frame MTU over LANX possible issues

Hi all!

So our business has two sites and over the years, jumbo frames (9000) have been enabled successfully at each site. End devices (PCs, servers, hypervisors, etc) are all sending large frames across the LAN and are working fine within that LAN.

However, recently we added a LANX in order to connect both sites to each other and allow hyperconverged systems to work more efficiently. Flat for a few VLANs, others are routed across using a specific VLAN for that purpose.

Problem is the metro ethernet doesn't support jumbo frames and I'm starting to think some of the connectivity issues across site we're experiencing are linked to this limitation. Seems to impact for flat and routed VLANs afaik.

So from my understanding:

• Large MTU frames are sent by the end device, when configured accordingly;
• L2 devices will drop the frame if too large; no fragmentation here;
• Fragmentation occurs at L3 only, requires router (or routed VLAN?);

So my question is: can it be configured for large frames to be fragmented before being sent over the LANX and how/where to do so, or are we in a pickle requiring we disable jumbo frames on our whole infrastructure, or at least all end devices?

Here is a brief topology of our setup:

End devices (9000MTU) <--> L3 switch (9000MTU system MTU) <--> LANX (1500MTU) <--> L3 Switch (9000 system MTU) <--> End devices (9000MTU) 

I hope the question isn't too trivial and thank you!