Linux\CentOS – Network – Full Qualified Domain Name on Comcast Home Network \ In-house DNS Server


I have a little home Network behind my Wireless Access Point.  But, lately one of the boxes that I need to access has been up and down.  And, I really need it to be up.

Quick Analysis

I am a bit disinclined to do heavy network troubleshooting. I just need things up; reliably and running.

What is wrong?

  • Is it a Comcast problem; btw Comcast is my ISP
  • Is it just this old LinkSys Home Router – I have it fronting the internal network; acting as a DHCP host, distributing IPs, and forwarding network packets based on Port Forwarding – Traffic Cop, the good one – Looks at Port# and sends it over to specific machines
  • Is it my Linux box (CentOS)
  • Is it an on \ off again Software Firewall on the Linux box

Usually, it wouldn’t bother me.  But, I really need to learn.

Comcast Network (thinking….)

I know I am entitled to 5 IPs from Comcast, and I have a spare one.

So for this one host that I need to communicate with, I will like to bypass the LinkSys Router and connect directly to the network switch that is connected to the Cable Modem

Comcast Network (Connected)

Once that connection is made, I have a good world reachable IP Address.  Hopefully, it will stay up and available.

Fully Qualified Domain Name

As the host is a box that will be running Hadoop, I know I need really good and firm FQDN.

What is the Network Domain Info

What is Comcast DHCP giving out?

Checked /etc/resolv.conf and have these entries:

Entry Value

What do we want it to be?

I really do not care much about the details.  But, I need to be able to control my destiny; which means having my own domain data:

Here is what we came up with:

Entry Value
nameserver ( DNS Server)

DNS Server Changes

Create A and “Reverse Lookup” entries for our Linux host.

Our DNS Server happens to be Windows-based, and we will just use a GUI to make the changes.

DNS - A Entry

Linux Node DNS Changes

On the Linux node, update /etc/resolv.conf with our updated DNS entries.

# Generated by NetworkManager


  • Our domain name is
  • Our DNS Suffix is
  • In our case, as we are getting an IP from Comcast and a homegrown network domain, we need to ensure that we choose our own DNS Server (that is also reachable over the Net).

Work Arounds

In case you do not have a good DNS Server or limited network addresses, please consider using a third party Dynamic DNS Provider.

My favorite used to be, but it seems that they are pulling back on free FQDNs.

Though I have yet to try, I have been hearing good things about it.


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