Preparing a validation for PR https://github.com/vyos/vyos-1x/pull/650 I noticed the following:

Given the following topology:

R1 uses a VLAN1 interface to to SW1, which uses the port as "trunk" interface. The switch used is an Arista vEOS-LAB device.

vyos@R1# show interfaces 
 ethernet eth0 {
     vif 1 {
         address 192.0.2.1/24
     }
 }

R2

vyos@R2# show interfaces ethernet 
 ethernet eth1 {
     address 192.0.2.10/24
     hw-id 50:00:00:04:00:01
 }

SW1

SW1#show run int eth1
interface Ethernet1
   description R1
   switchport mode trunk

SW1#show run int eth2
interface Ethernet2
   description R2

SW1#show run int eth3
interface Ethernet3
   description VPC

The devices can not ping each other. As soon as I move the address on R1 from VIF1 to the interface itself, traffic starts to flow. Is this expected? If so, why support a VIF of 1?

Update

Changing SW1 eth1 port to switchport trunk native vlan 10 made it work as the switch was still accepting untagged vlan1 packets.
On VyOS side:

• ethernet eth0 address 192.0.2.1/24 generates untagged packets
• ethernet eth0 vif 1 address 192.0.2.1/24 generates tagged packets in vlan 1