Each PPPoE client policy allows configuration of both MRU and MTU. The MRU is sent toward the peer during the discovery phase. If any of the MRU or MTU is bigger than 1492, the Max-Payload tag is included and is set to the maximum of the configured MRU and MTU values.
Upstream data packets are subject to the smallest of either the received MRU or the configured MTU. The node fragments IPv4 packets without the DF flag set and drops IPv6 packets and IPv4 packets with the DF flag set. For the packets with the DF flag set, appropriate ICMP or ICMP v6 error messages are sent.