Ethernet Speed Problems - ePMP3000 / Force300-16

I have a strange issue with my new ePMP3000 base.

A client has a Force300-16 hung at their house about .5 miles away from the tower. 

The radio is plugged into a R201P and running PPPoE. 

When they speedtest over wireless, everything works great. User is on a 50meg down, 20meg up., They get arund 48meg down, and 18 meg up. 

When they test over ethernet, they get .6meg down and 18 meg up. 90% of the time. The ping times jump from 6ms to 280ms over multiple tests but I still get stuck on having an extremely low downspeed. 

I thought at first it was the router, but we replaced the router with an EDIMax router, and issue persists. 

If I take the router out of the equasion,  plug directly into the radio and run PPPoE behind it, I dont see the issue at all. It only happens when I've got a router behind the radio.

I've tested this with the last stable and the latest RC-Beta on the base and the clients. 

i observe this behavior on epmp 1000 too still scratching my head to find the problem.  

check and see if those routers have mmsclamping enabled.   mayhave an MTU issues going on. 

We had a similar problem with the PTP 550 (brother to ePMP 3000/300). We got them in last week and and did a quick set up using a SOHO router. Setup was like this Fiber>Mikrotik>Master<>Slave>SOHO>devices. Devices wired to SOHO had good speed tests and latency (in relation to router we were using). Devices connecting to SOHO wireless had slow speeds (around 15Mbps up and down) and ping times from laptop to master varied from 3ms to over 200ms. SOHO was on 2.4 band so no self interference. Threw a cheap 1 gig Netgear switch between slave and SOHO and issue went away. 

I am not a networking guru (we contract the heavy networking for now) so I only have a good guess to why this is. I am sure someone like Chris Bay, Newkirk, and others could probably tell you down to the packet what the issue is/was.

Not too concerned, the 550's seem to work fine when connected directly to Mikrotik routers, which is how they will be ran when released into the wild. For anyone wondering, when set up using tik routers, using 20Mhz+20Mhz channel bonding, we were seeing speed tests (AT&T speedtest) of 240+Mbps down and 60+Mbps up (MCS9 all around). On other speed test sites we were getting 150-200+Mbps down. Pretty good for a single pc speed test. 

I adjusted the mtu manually on the end point computer and still had the problem. I'm not surewhat mmclamping is.....I've never seen those settings. One router is a R201P and the other an EDI Max AC1200....

>I'm not surewhat mmclamping is....

Pretty sure he meant MSS Clamping. 

As much as I love about PPPoE  I really hate the MTU issues that crop up from time to time these days. We used it for many years without a problem really but in the last 3 years it seems like we are constantly dealing with some new problem (it always breaks the streaming services ... always) caused either by something the CDNs changed or Miktrotik and Cambium updates breaking stuff.