Listen on VLAN using an appropriate BPF filter and VLAN decapsulation.
Three cases may happen:
- You have a non VLAN accelerated network card.
The BPF filter will catch the frames in the VLAN and the frame will
be decapsulated.
- You have a VLAN accelerated network card and a kernel < 2.6.27.
lldpd won't see any frame encapsulated into a VLAN.
- You have a VLAN accelerated network card and a kernel >= 2.6.27.
lldpd will see the frames encapsulated into a VLAN as untagged
frames and won't need to decapsulate them.