I'm running CentOS-6 on an HP MicroServer (since this morning) and I'd like to open an non-standard port, for use on a laptop attached to the internet through the server. Do I have to explicitly add an iptables rule? If so, and I want to open (say) udp port 500 , what command should I give? I've always used shorewall in the past, and will probably do so now if the default firewall is difficult to use. But I thought I would try it first as an experiment. My recollection is that in old versions of CentOS one could non-standard ports through system-config-firewall ; but it seems that now this can only be used for standard ports; I looked at <http://wiki.centos.org/HowTos/Network/IPTables> but didn't find it very enlightening. Any advice or suggestions gratefully received. -- Timothy Murphy e-mail: gayleard /at/ eircom.net tel: +353-86-2336090, +353-1-2842366 s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland