Security Level question
 

I run into wierd condition - after I installed RH9.0 - let's name it RH (with security level set to High with no trusting devices )and roaring pppoe client (with firewalling set to masquerade).
Now I want to add additional 2 comps and of course I want them surfing the net.
I tryed to connect to RH from other station and I failed to do this. Oings are ok but no more. nmap shows no ports open. First I thought about firewalling of pppoe client - but I did't find anything in config files exept one row in /etc/sysconfig/network-scripts/ifcfg-ppp0 that says "FIREWALL=MASQUEADE". How the control is done? ipchains is not installed and iptables do not contain nothing related?
Next I discovered that the problems of ports blocked were due to setting Security level to High with no trusted devices. Is this normal? (it again is not reflected by iptables of whatever - so which file is possesing the configuration data).

And the main question - what should I change in Security Level and Firewalling parameters in rr-pppoe client in order to get things work? (iptables I will configure - it's not a problem).

Thanks in advance for any help.