This morning I did a manual yum update on our a mail server to 7.1
without any incident or problems. A new kernel was installed, and I
rebooted after the update.
When I rebooted the machine I could not gain SSH access to it from an external ip address. I was able to SSH to this mail server through a different machine on the local network.
At first I thought the problem was related to the firewall. I stopped firewalld, and fail2ban, and clear all firewall rules without being able to gain access.
I disabled firewalld, and fail2ban. I enabled iptables and started it without a problem, but I could still not gain access. I removed all entries in the host.allow and host.deny files, and this did not make a difference either.
On one of the various reboots I tried to use the previous kernel before today’s update, but there was no success.
I can scan the mail server and reach it without a problem from the internal network but I am not able to reach it from outside the local network. I have the mail server behind a Centso 5.11 machine that is the gateway router for the internal network, and the mail server is nat addressed with it’s external ip address to the internal machine. I have had this configuration set up for over 7 years. I tweaked the Gateway router to nat address the mail server’s ip address to a different machine inside the network and everything worked perfectly like it should, and then re-adjusted the gateway router again back to the mail server and am not able to gain access from outside the local network.
“traceroute” does not get to the mail server from outside the local network, but works fine inside the local network.
Bottom line, this does not look like a host.deny, host.allow problem, nor does it look like a firewalld or iptables problem. And it does not appear to be a problem with the gateway server.
Is there another feature of CentOS 7.1 that I need to evaluate? Has anyone else had this problem after the 7.1 update?
Thank you for your help!!!!