Latest LQ Deal: Complete CCNA, CCNP & Red Hat Certification Training Bundle
Go Back > Forums > Linux Forums > Linux - Server
User Name
Linux - Server This forum is for the discussion of Linux Software used in a server related context.


  Search this Thread
Old 05-19-2011, 09:36 AM   #1
LQ Newbie
Registered: Dec 2006
Location: Florida
Distribution: Ubuntu and CentOS
Posts: 23

Rep: Reputation: Disabled
Internal and External DNS

Hello everyone,

Here is probably an easy question if anyone can help me out. I have done tons of reading but nothing really helps answers this question: What is purpose of Internal and External DNS?

I know you need DNS to translate computer/server names to IP addresses and store the records. So why do you need 2 internal and 1 external DNS? I do understand about having an internal DNS for internal network but what about the external DNS?

Also, why do you need 2 DNS inside the network? Can you have one internal DNS and make that your primary and if it can't find the record then have that one point to your external DNS in the DMZ?

Am I making some sense or am I just confused? I think I need a quick school lesson on DNS. I feel embarrassed to ask. Thanks for all of your help.
Old 05-19-2011, 10:36 AM   #2
LQ Guru
Registered: May 2005
Location: Atlanta Georgia USA
Distribution: Redhat (RHEL), CentOS, Fedora, CoreOS, Debian, FreeBSD, HP-UX, Solaris, SCO
Posts: 6,986
Blog Entries: 14

Rep: Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187Reputation: 1187
There is no "requirement" for:
1) More than one DNS server.
2) Separate internal and external DNS servers.

There are however "best practices".

The main reason for more than one DNS server is redundancy. If one goes down and the other is up queries will still work. If you only have one when it is down then most things (because most things rely on name resolution) will break because they can't find the IP address they are requesting from DNS.

One reason for separate internal and external DNS servers is that the IPs you use internally might not be the ones you use externally (they seldom are - often you'll have a 10.x or 192.x network internally but your web servers etc... will be in a public IP range [often NATted from the internal IPs]. Also there are security implications. You don't want a DOS attack on your external network affecting your internal operations. Also you don't want people outside your network seeing all the devices you have inside your network and finding out their IPs. Typically the external DNS is in the DMZ. Also you might be doing Dynamic DNS updates on your internal server using DHCP.

However, you CAN (but shouldn't) make one server both the internal and external server and can even set separate IPs ranges to use for internal and external using "views".

Edit: Another reason to separate internal and external. Often you want to allow your internal users to query cache and/or do recursive queries. You do NOT want external users doing that due to cache poisoning attacks.

Last edited by MensaWater; 05-20-2011 at 10:15 AM.


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
internal and external DNS configuration in RHEL5.3 or RHEL5.4 edu kiai Red Hat 4 05-04-2011 08:34 PM
Internal host names resolving through external DNS?!? dschuett Linux - Networking 2 02-06-2011 03:14 PM
DNS resolution for internal and external clients bobbera Linux - Server 5 11-24-2010 08:46 AM
dns with internal and external views settings cool47 Linux - Networking 1 05-25-2008 04:20 PM
Can bind 9 (DNS) resolve names based on who's asking?? (internal vs. external clients registering Linux - Networking 3 06-16-2004 07:25 AM > Forums > Linux Forums > Linux - Server

All times are GMT -5. The time now is 06:06 AM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration