i have installed proxmox on my laptop which has one interface and an additional usb to ethernet adapter.and opnsense on the proxmox.the inbuilt ethernet adapter is configured as LAN and usb adapter as WAN.currently i am able to get only 9Mbps internet speed.my isp plan in 250Mbps.any suggestion what i am doing wrong.i am using pppoe.
Configured like what? There are bazillions of possibilites, like pass-through or virtio andy many more.
See:
https://forum.opnsense.org/index.php?topic=42985.0
and:
https://forum.opnsense.org/index.php?topic=44159.0
yes it is configured as virtio.
Did you work through the network "hardware" section in the guide?
Does the USB network adapter show full link speed? 9 Mbit/s could either be 10 Mbit/s on the ethernet side or an inferior USB link, like with USB 1.1.