On 12/11/2014 09:35 AM, Warren Young wrote: >> Am 11.12.2014 um 04:48 schrieb Warren Young: >>> the stock configuration of Apache only listens for IPv6 connections: As per RFC 3493 (Sections 3.7 and 5.3) an IPv6 socket will accept connections from IPv4 hosts, which will be mapped into the IPv6 address space. > We noticed this problem when web browsers would refuse to connect to the server. *Then* we discovered the netstat oddity, and *then* we found that changing the Listen line in httpd.conf fixed it. > > That leaves me still wanting an explanation for what happened. > > New guess: there’s a difference between the IPv4 and v6 firewalls, so that changing the Listen line caused Apache to avoid the problem on the v6 side. I don't have a good guess, there. If the client was actually connecting from an IPv4 address, then the IPv4 firewall rules should have applied. At least, that's what my testing indicates. What I can say for sure is that a CentOS 7 system will accept IPv4 http connections if the IPv4 firewall allows that port, or if the firewall is disabled. Whatever problem you faced was caused by post-install configuration. Try making your standard changes incrementally and testing as you go until you can locate the steps where the problem occurs.