I experienced an odd thing the other day when I went to reboot a server it was hanging at bootup at the iptables/firewall portion of the startup sequence.
I had to do “Interactive” bootup (by hitting “I”) and then I could say “n” on the firewall section. After that it booted up fine.
I examined my iptables and some postings on the ‘net will mention that failing to have the loopback interface in the rules, i.e. “-A RH-Firewall-1-INPUT -i lo -j ACCEPT”. I verified I had that, and then I realized that I also had a rule in place that was generated by an auto-rule script that uses IPs from failed attempts in log files. Somehow it had gotten 127.0.0.1 in there! I had to remove a blocking rule for 127.0.0.1 and then it worked.
So, rule of thumb, take care of what goes in your iptables file!