https://cloud.google.com/interconnect/docs/how-to/dedicated/configuring-onprem-routers
I switched the GCP Dedicated Interconnect. What I need to configure is the onprem-router. However, the MTU value of my switch is the minimum value of 1500 although the Guide has an MTU value of 1440. Is the GCP router only different because it is a virtual router of SDN? It doesn't matter if you set the MTU for the onprem-router at 1500? Is the MTU of the VM ROUTER on the GCP only the value of Rayload?
As GCP router is SDN, it needs a little overhead in order to get the packets trough GCP network. If you set the MTU higher than 1440 on your onprem-router your Cloud router might drop or disable packets which have a bigger MTU.
I found this documentation regarding a Cisco router option that should decrease the MSS size thus making the packet smaller, but I'm not sure that would solve your issue as the MTU announced by your router will still be 1500 and the MTUs need to match for most efficient use of Cloud Interconnect.
