Does my computer have firewall?
 

Sorry for stupid question, but I need to know, whether my RHEL 5.8 has active firewall. I didn't install any firewall, does RedHat has built-in firewall? If yes, how can I check, whether it is enabled or not?

the Linux kernel contains NetFilter which is the "firewall" functionality. It is tuned and configured using the iptables tool. You have it. As to it running or not, run "service iptables status" to check, and also list the current rulebase (stored in /etc/sysconfig/iptables) by running "iptables -vnL". You can use the system-config-firewall or security-config-securitylevel (it changed between RHEL versions but I forget which one you'll have) to do *very* basic changes to it.

Thank you.

Just to be sure: does this mean, that firewall is not active?

I found System - Administration - Security Level and Firewall command, it allows to enable/disable firewall.