Solved

Ubuntu Server Won't Resolve Hostnames

Posted on 2014-02-18
10
1,673 Views
Last Modified: 2014-02-20
Just installed a fresh build of Ubuntu Server 12.04.4 x64 to find that I can't get DNS functionality to work.  In the configuration wizard, I entered the name server of 8.8.8.8.  I can successfully ping this IP and can see its entry in /etc/resolv.conf and /etc/network/interfaces.  But I can't perform nslookup or ping any hostname.
0
Comment
Question by:marrj
  • 3
  • 3
  • 2
  • +2
10 Comments
 
LVL 21

Expert Comment

by:Mazdajai
Comment Utility
Is iptables running? What is your network configuration?
0
 
LVL 1

Author Comment

by:marrj
Comment Utility
I'm fairly new to Linux.  How do I tell if iptables is running?

By network configuration, do you mean the content of the /etc/network/interfaces file?
0
 
LVL 48

Expert Comment

by:Tintin
Comment Utility
What's the output of

iptables -L
0
 
LVL 21

Expert Comment

by:Mazdajai
Comment Utility
Yes. Beside iptables provide the following -

dig google.com 8.8.8.8

Open in new window

0
 
LVL 13

Expert Comment

by:Sandy
Comment Utility
Also check with your network guy whether port 53 is open or not to allow name resolution.

TY/SA
0
Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

 
LVL 8

Expert Comment

by:Surrano
Comment Utility
Instead of asking to open port 53 I'd recommend to ask your network team to give you a proper DNS IP within the intranet. Tends to be more friendly and less prone to future nasty comments from network team :)
0
 
LVL 1

Author Comment

by:marrj
Comment Utility
Output from iptables -L

Chain INPUT (policy ACCEPT)
target     prot opt source     destination

Chain FORWARD (policy ACCEPT)
target     prot opt source     destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source     destination




Output from dig google.com 8.8.8.8

;; global options: +cmd
;; connection timed out; no servers could be reached
;; connection timed out; no servers could be reached



I happen to the be the network guy, and I am certain that outbound TCP53 is open at my ASA.  This server is going to be in a DMZ, and I really don't want to open up anything from the DMZ to the inside that I don't have to.  I've also got a static NAT created at my ASA for this machine.  As I said, I can ping any IP (public or private) that I want to.  I just can't perform name lookups.  I don't think it's a NAT or port issue.  I've got a Windows server set up the same way and have no problems performing nslookup on 8.8.8.8.
0
 
LVL 48

Assisted Solution

by:Tintin
Tintin earned 250 total points
Comment Utility
Make sure you have UDP 53 opened on the ASA.   Most DNS queries are over UDP rather than TCP.
0
 
LVL 21

Accepted Solution

by:
Mazdajai earned 250 total points
Comment Utility
>>I've got a Windows server set up the same way and have no problems performing nslookup on 8.8.8.8.

Can you confirm the Ubuntu server and the Windows are in the same subnet? As well as UDP53 is open?
0
 
LVL 1

Author Comment

by:marrj
Comment Utility
I decided to reinstall the OS from scratch.  Now, DNS works fine.  Strange.  Thanks for your help.
0

Featured Post

Highfive Gives IT Their Time Back

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

Join & Write a Comment

Suggested Solutions

Little introduction about CP: CP is a command on linux that use to copy files and folder from one location to another location. Example usage of CP as follow: cp /myfoder /pathto/destination/folder/ cp abc.tar.gz /pathto/destination/folder/ab…
In my business, I use the LTS (Long Term Support) versions of Linux. My workstations do real work, and so I rarely have the patience to deal with silly problems caused by an upgraded kernel that had experimental software on it to begin with from a r…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

8 Experts available now in Live!

Get 1:1 Help Now