linuxbridge+vxlan,the vm can not download big file from external network

edit

i install an private subnet with linuxbridge+vxlan，the vxlan vm has the mtu 1450；i can upload big file to the external network form vxlan vm，but can not download big file from external network；i tried the mtu trouble-shooting，but can not solved it。i think maybe there is some bandwith limiting setting by default，but can not figure it out，please help me。