You can get full control of all iptables modules on ComfortVPS Xen VPS. How to load iptables modules in Xen VPS?

First, you need install modules, eg

[root @ comfortvps]# modprobe ipt_limit
[root @ comfortvps]# modprobe ipt_LOG

Then, confirm the modules isntalled:

[root @ comfortvps]# lsmod | grep ip
ip_conntrack           53665  0 
nfnetlink              10713  1 ip_conntrack
ipt_LOG                10049  0 
x_tables               17349  2 xt_limit,ipt_LOG
ipv6                  273057  16 
xfrm_nalgo             13381  1 ipv6
dm_multipath           27213  0 
scsi_dh                12481  1 dm_multipath
dm_mod                 63993  4 dm_mirror,dm_multipath,dm_raid45,dm_log

Then you can use it on iptables.