I have a Zyxel P870 connected to VDSL2. With my laptop doing the PPPoE authentication the MTU is measured (using ping -f -l ...) at 1480 bytes and speedtest (speedtest.net) is good, 49/6. However with the RB1200 doing the PPPoE authentication and nat routing to laptop the laptop measures the MTU at 1300 bytes and speedtest is poor, 6/6 at best. I didn't expect the throughput to drop so dramatically and was wondering if someone could enlighten me as to why the MTU reduces by 180 bytes and resultant fragmentation reduces the throughput dramatically.Thanks
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