With the new Bastille version it is now FINALLY possible to assign a fixed MAC address to a FreeBSD jail. This is helpful if the IP addresses are assigned via DHCP (as is the case with me). Here we go.

New Jails

To create a jail with a fixed MAC address, it is sufficient to specify the new parameter -M when creating the jail.

Old Jails

But what about the existing jails? Three new lines are required in jail.conf, which are located below the exec.prestart += "ifconfig epairXb up name eXb_JAILNAME"; line:

JAILNAME should stand for itself, the meaning of MAC-A and MAC-B must be explained:

• VTNET jails have two virtual MAC addresses
• MAC-A is on the bridge and MAC-B on the jail, which is then also visible on the DHCP server
• eXa: The X must be replaced by the number that has already been used for the other entries

Simply replace the last digit with a and b, then you have your pair:

• MAC-A = 8b:75:d6:46:c6:4a
• MAC-B = 8b:75:d6:46:c6:4b

Because you edit the respective configuration, e.g. /usr/local/bastille/jails/db/jail.conf

  exec.prestart += "ifconfig eXa_JAILNAME ether MAC-A";
  exec.prestart += "ifconfig eXb_JAILNAME ether MAC-B";
  exec.prestart += "ifconfig eXa_JAILNAME description \"vnet host interface for Bastille jail JAILNAME\"";

In this example, it looks completely like this:

db {
  enforce_statfs = 2;
  devfs_ruleset = 13;
  exec.clean;
  exec.consolelog = /var/log/bastille/db_console.log;
  exec.start = '/bin/sh /etc/rc';
  exec.stop = '/bin/sh /etc/rc.shutdown';
  host.hostname = db;
  mount.devfs;
  mount.fstab = /usr/local/bastille/jails/db/fstab;
  path = /usr/local/bastille/jails/db/root;
  securelevel = 2;
  osrelease = 14.2-RELEASE;

  vnet;
  vnet.interface = e8b_db;
  exec.prestart += "ifconfig epair8 create";
  exec.prestart += "ifconfig publicnet0 addm epair8a";
  exec.prestart += "ifconfig epair8a up name e8a_db";
  exec.prestart += "ifconfig epair8b up name e8b_db";
  exec.prestart += "ifconfig e8a_db ether 8b:75:d6:46:c6:4a";
  exec.prestart += "ifconfig e8b_db ether 8b:75:d6:46:c6:4b";
  exec.prestart += "ifconfig e8a_db description \"vnet host interface for Bastille jail db\"";
  exec.poststop += "ifconfig publicnet0 deletem e8a_db";
  exec.poststop += "ifconfig e8a_db destroy";
}

At the end, it is sufficient to restart the jail with bastille restart JAILNAME.
If the MAC address is registered accordingly in the DHCP server, the same IP is always assigned.