And check. Zaram works on the 4 Gbit KPN line.
Speeds are 4 up and almost 4 down. Cpu load is around 10% at full speed.
temps are around 45 degrees Celcius
I,m happy with it 
There was a renaming in the openwrt device tree, now that the kernel made it possible for openwrt to have those custom names as part of the device tree.
Eth0-X are the default names given by the kernel.
But on the PCB and the case they are called LAN and WAN and since they are sfp modules they decided to call them sfp-lan and sfp-wan, which totally makes sense to me.
it makes sense to me now too
not saying that its a good thing to do without anyone knowing before one is confronted with it.