Draytek 2860 as Bridge modem (FTTC) to Ubiquiti Edge Router 3 Lite - MTU question

[#1]

Hi Guys,

Looking for a little help, I am using a Draytek 2860 as an expensive bridge modem (had one spare) linked to a Ubiquiti Edgerouter 3 Lite. I have seen in various posts that I can use a 1500 MTU without using MSS Clamping in the edgerouter and everything should work fine, If I set the ETH0 interface on the edgerouter to have an MTU of 1508, then the PPPOE link on the edgerouter to 1500 MTU and then the draytek 2860 WAN MTU to 1500 some websites load and others fail, the only way round this is to set MSS clamping in the edgerouter to 1452 MTU.

Is this correct or am I doing something wrong, I have seen posts saying that using a 1500 MTU removes the need for MSS clamping, can anyone clarify if this is correct, if so, any ideas where I am going wrong.

Thanks in advance John.

[#2]

@jtankard

My suggestion would be an email to Draytek. I made one support contact a while back and as I recall they were very helpful. There is a UK operation which is where I would start.