Hi, this commonly happens by incomplete network configuration in either the host and/or the bastille.conf file if missing parameters.
A simple solution for basic/shared IP jails, as of later bastille updates it added the ability to specify any system available network interface during jail creation, by explicitly specifying it after the IP address e.g:
Usage: bastille create name release ip | interface.
where "interface" can be either an lo1, em0 etc., if the network interface pass validation , the created jail will use this NIC for simple/shared IP based jails unless vnet configured, but be aware that bastille does not care is this external NIC is active or not.
Second option, under bastille.conf file, setting an external NIC e.g: bastille_jail_external="em0" will tell bastille to always use this NIC when creating jails unless override by the first option above.
Third option is for a more complex/specific network scenarios such vnet, ipv6, firewall etc., it requires for more advanced manual work by the user in the host, the jail/jail.conf etc.