Can't access Nagios via URL

[NagiosNewb74]

I am new to Nagios and everything Linux. I have setup a CentOS 6.4 on a VM and installed Nagios Core 3.5.0 and Plugin 1.4.16. I also did a su -c 'yum update'. I followed the instructions in installing nagios from source (http://assets.nagios.com/downloads/nagi ... Source.pdf) to the letter and without incident. All teh pre-checks work and it sems like everything is ok. However when I try to access the host via http://ip/nagios/ I get nothing. I've tried multiple browsers as well as from another device on the same subnet. I was able to subbecfully configure cntlm in order for the nagios box to retrieve updates via the ISA proxy server. I have full name resolution out from the box. I recall seeign soemthing about it not beign able to register it's hostname and will be using localhost.

I've had a look for similar postings and also did the yum install nmap and nmap localhost -p 80. It indicated that the port is open. I have some fundamental issue with Apache I suspect but don't know what it could be.

I was led to believe that CentOS would be one of the easier Linux distributions to use but I'm now wondering if I should be usign something else?

[NagiosNewb74]

After some assistance from someone in the know, I discovered the issue was the Apache firewall and iptables. I've now turned this off and I can access the web interface.
Why this is not included in the setup instructions is a mystery to me.

[abrist]

CentOS is usually really good about ports and services. Most of the time, the rules are created automatically, and the ports are opened when the service is brought up through systemd. Did you choose to install a 'hardened' version of Cent? How was nagios installed?