This tutorial by user shows us how to get VLAN set up in a FreeBSD jail. See the link below for the full instructions.

This article discusses how to set up jails on a FreeBSD 11-CURRENT system utilizing VIMAGE (aka VNET) to provide a virtualized independent network stack for each jail with support for VLAN tagging.

Prerequisites

  • You have a machine installed with FreeBSD 11-CURRENT on ZFS.
  • We will be building world and kernel and using that as the base for the jails. Hence basic knowledge of FreeBSD system administration is assumed. If you’ve never compiled and installed a FreeBSD base system and kernel, this article may be hard to follow. Refer to the FreeBSD Handbook, especially chapter 8: ‘Configuring the FreeBSD Kernel’ and chapter 23: ‘Updating and Upgrading FreeBSD’.

Assumptions

  • Your host’s ethernet interface is em0.
  • Your IP network is 192.168.6.0/24 with gateway at 192.168.6.1.
  • The host will be assigned IP 192.168.6.66.
  • The guest jails will be assigned IPs in the range 192.168.6.100-254.
  • VLAN ID for all network interfaces will be 6.
  • Jails will be stored in ZFS datasets under /jail directory.

Configure the host system …

Full tutorial: https://gist.github.com/sdebnath/086874c5df8b68e0df69