choppyc1d
I've been trying to get baby jumbo frames to work mtu 1508, when I putty in and ip link list, everything shows as mtu 1500, with the exception of pppoe-wan which shows as 1492, I've tried to change it in ssh, with ifconfig pppoe-wan mtu 1500 but then the internet is very slow, my modem mtu is 1520, anyone have any ideas? I cannot see on interface where I can alter pppoe mtu, without putty, please help!
You need to set the underlying interface to (at least) MTU 1508. So e.g, eth0.2 has MTU of 1508. Then you can set the PPPoE-WAN interface to an MTU of 1500. If your ISP accepts that 
The MTU of 1508 can be set in the /etc/config/network configuration file if everything works. Better to have an PPPoE up script to (reset) that interface for an MTU of 1500.