Ethernet Adapter in New CentOS 7 Server Not Working

[harryalder]

HI,
I have only been working with Linux for a little less than two weeks so if I don’t say something in exactly the right way, please be kind and just ask me again. Secondly, the issue I believe that I am having, has to do primarily with my new server’s external network card. A little background here would probably help. I originally built this server with two Ethernet adapters; one was for internal use which has a 192.168.xxx.xxx private internal address. The second card was on an address (96.93.196.241) from one of the public IP blocks that we lease from Comcast Business and was for external access to our website. Everything appeared to be working and I could SSH into the server using either address from a workstation here. I could also get to a test index page for our site from the workstation using either the Internal or External address of the server. I later assumed that the reason I could get to the external address was because that IP belongs to a block of addresses that we use here for other servers and firewalls and that our main firewall or Comcast was routing the request internally since the firewall is on the same subnet as this server. (This server is not connected to a firewall other than the internal firewalld in the CentOS). When I tried to install a Let’s Encrypt security cert, the authentication procedure timed out. I contacted Let’s Encrypt and Danial figured out that my site could not be reached from the outside of my office. After a couple of days with Danial providing excellent advice, we could not solve the problem. Danial said that he just wasn’t that familiar with CentOS 7 to be able to help me troubleshoot my issue. I completely understood that so I deactivated the local card and changed ONBOOT to NO so that it would not load the card every time I rebooted. I then proceeded to troubleshoot the external card. At first the card would really do nothing. I could not reach any website nor could I ping any external address including the ISP’s Gateway address assigned for this IP block. I know that if you can’t ping the gateway for the card, you are really not going anywhere. I found that there was a /24 or 255.255.255.0 subnet showing in ifconfig when I did an ifconfig -a from the command line. The ifcfg-enp8s0 file however, showed the correct subnet /28 or 255.255.255.240. The correct value /28 also appeared in the nmtui utility when I checked the status of the card. I have no idea why it showed up incorrectly in the ifconfig screen when it was correct in the other two places. Anyway, I got that fixed and that brings us up to date as to where we are now. The internal card is deactivated and I can ping the stated gateway address for the IP I am using. I cannot ping other outside addresses nor reach any website using DNS or the site’s direct IP address.

I am sorry that this was so long, but I wanted to provide an understanding of the whole picture. I am now wondering if there might be a routing problem. I’ve looked at the iptables and have no idea what I am looking at. I’m at a bit of a loss at this point. Any help that you could provide me as to where to go from here (be careful now) would be more than greatly appreciated.

Again, thanks for your reply and your help in advance.

Harry
Golden, CO, USA

[harryalder]

Here's a little additional info. Here is what I get when I do a "route -n" request:


Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
96.93.196.240 0.0.0.0 255.255.255.240 U 0 0 0 enp8s0
169.254.0.0 0.0.0.0 255.255.0.0 U 1003 0 0 enp8s0
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0

The network card in the server has:

IP Address=96.93.196.241
Gateway= 96.93.196.254
Subnet Mask=255.255.255.240

Table doesn't look right but I don't know why.

Hope this helps.

Harry