this is what I get by trying this procedure
JAIL_NAME:caddy: not found
JAIL_INTERFACES not set, defaulting to: vnet0:bridge0
caddy successfully created!
Stopped caddy due to VNET failure
Failed to create jail
the parameters I entered
JAIL_IP="192.168.1.192"
DEFAULT_GW_IP="192.168.0.254"
POOL_PATH="/mnt/Stockage"
JAIL_NAME:"caddy"
in general when I create jails in command line, this procedure works all the time
iocage create -n nextcloud -r 11.3-RELEASE ip4_addr="vnet0|192.168.0.10/24" defaultrouter="192.168.0.1" vnet="on" allow_raw_sockets="1" boot="on