ePMP3000 series which cannot ping date size more than 1472Byte ，but for ePMP1000/2000 series can
When the MTU on the network is set to default MTU(1500) we will not be able to ping packet size set to more than 1472
I see that epmp devices are default 1538… should one replicate this on edge routers and switches if they are default 1500?
In my opinion keep 1500 and set the same on 3000
Depending on what your doing network wise, no you would not duplicate that.
To prevent fragmentation you use a larger MTU in your backhaul and core networks to your gateway. Customers usually use equipment that expects frames to be 1500 bytes or less.
1538byte is the full frame default size after all headers are attached. We set customer MTU at 1500 but run 1700 on our APs, ptp links, switches and routers. This allows us to send large frames when sending backups to our DR NOC (which makes better use of the ptp links) but still keep client MTU smaller than our fragmentation threshold. Remember that packet fragmentation slows down your switches and routers so best to plan for it.