первые 250 стартуют:
real	2m20.408s
user	0m29.224s
sys	1m40.088s
[root@fbsd /usr/local/sbin]# jls | grep -e [[:digit:]] | wc -l
     251

[root@fbsd /usr/local/sbin]# cat jails.sh 
#!/usr/local/bin/bash
for i in `seq2 -s 2 -e 250`; do
  ifconfig msk0 alias 192.168.1.$i
  ezjail-admin create -r /usr/jails/j$i.izhnet.org j$i.izhnet.org 192.168.1.$i
done