Anyone runs MPLS Traffic through a CRS317? I get packets >1500 dropped. (I dont use dont Fragment bit set when pinging).

I reduced the scenario to a minimum. I need a chain of Routers for MPLS to encapsulate Packets. As soon as I plug a 317 in between with 2 Ports untagged into the same vlan packets get dropped > 1500. Replacing CRS317 with another switch the problem disappears immediately. Without MPLS I dont see this problem. Packets > 1500 get fragmented and got through.

I tried to increase MTU on the CRS317 which does not help.