The virtual device does not appear to be detected.
Both VMs have a network adapter with SR-IOV enabled.
VyOS:
vyos@VyOS:~$ sudo su root@VyOS:~# lspci root@VyOS:~# lsmod | egrep "(hv|hyper)" hv_balloon 40960 0 hv_utils 49152 2 hv_storvsc 28672 1 scsi_transport_fc 102400 1 hv_storvsc hv_netvsc 114688 0 scsi_mod 303104 6 sd_mod,hv_storvsc,scsi_transport_fc,usb_storage,sg,sr_mod hyperv_keyboard 12288 0 scsi_common 16384 6 scsi_mod,sd_mod,hv_storvsc,usb_storage,sg,sr_mod hv_vmbus 172032 5 hv_balloon,hv_utils,hv_netvsc,hv_storvsc,hyperv_keyboard
Fresh Debian install:
root@Debian:~# lspci 4caf:00:02.0 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function] (rev 80) root@Debian:~# lsmod | egrep "(hv|hyper)" pci_hyperv 40960 0 pci_hyperv_intf 16384 2 pci_hyperv,mlx5_core hid_hyperv 16384 0 hv_netvsc 106496 0 hid 155648 2 hid_hyperv,hid_generic hv_utils 49152 2 hv_balloon 40960 0 hv_storvsc 24576 3 scsi_transport_fc 90112 1 hv_storvsc scsi_mod 274432 4 sd_mod,hv_storvsc,scsi_transport_fc,sg hyperv_keyboard 16384 0 hyperv_fb 24576 1 scsi_common 16384 3 scsi_mod,hv_storvsc,sg hv_vmbus 151552 8 hv_balloon,hv_utils,hv_netvsc,hid_hyperv,hv_storvsc,hyperv_keyboard,pci_hyperv,hyperv_fb }