The Layer 2 access concentrator (LAC) DF bit is configurable, but by default, it sends all L2TP packets with the DF bit set to 1. Clearing the DF bit allows downstream routers to fragment the L2TP packets. The LAC itself does not fragment L2TP packets. L2TP packets that have a larger MTU size than what the LAC egress ports allows are dropped. The DF bit can also be configured through RADIUS attribute Alc-Tunnel-DF-bit.