Solved

DNS possible cause of slow response

Posted on 2015-02-09
6
122 Views
Last Modified: 2015-02-16
My users are complaining of slow response accessing the Internet and accessing the application on the internal server. The slow response seems to happen in early afternoon. I am trying to narrow down the troubleshooting process. I am trying to eliminate the DNS as a possible cause of the poor performance. Is there any tool I can use to look at the latency for the name resolution for the internal DNS? Thanks
0
Comment
Question by:leblanc
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
6 Comments
 
LVL 78

Accepted Solution

by:
arnold earned 250 total points
ID: 40599406
If you have your own DNS server, make sure if you use forwarders that those forwarders are still valid. Better still, note the forwarders, and remove them and see whether that changes the resolution part.

run nslookup -debug www.

depending on your connection, you might be able to monitor usage to see whether your WAN is saturated when this issue comes up.
0
 
LVL 1

Author Comment

by:leblanc
ID: 40599526
What are forwarders?

"depending on your connection, you might be able to monitor usage" How do you monitor the usage of the DNS resolution? Thx
0
 
LVL 78

Expert Comment

by:arnold
ID: 40599615
check your internal name services to see whether it is configured to use external DNS servers to which oit will forward received requests.

You can use network monitor tool or wireshark on the dns server to see whether it is being inundated by requests and the source.
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 57

Assisted Solution

by:giltjr
giltjr earned 125 total points
ID: 40599916
forwarders are DNS servers that your DNS server is configured to forward requests to when your DNS server does not know the answer.

Your DNS server know the host names for all hosts within your domain, but it does not know ALL hosts in the Internet.  For example your DNS server does know the IP address for www.experts-exchange.com.  So when your computer asks your DNS server   to look up the address for www.experts-exchange.com, it needs to pass the request to another DNS servers.

Normally you would configure your DNS server to forward to DNS servers that your ISP provided you with.  Otherwise your DNS server would need to have what is called the root hints file.  This is a list of the root DNS servers on the Internet.
0
 
LVL 78

Assisted Solution

by:arnold
arnold earned 250 total points
ID: 40599967
the bandwidth consumed by dns queries are insignificant these days to justify the use of forwarders as giltjr so kindly explained.
forwarded requests/responses might not be cached such that if your users accessing similar resources from similar sites, with forwarders they do not benefit from faster secondary responses which without forwarders will be returned from the local DNS cache.
It is possible that one of the ISPs DNS servers you have is being fixed, being hit with many other requests from other users, setups such as yours.

to get the list for hints on a linux/unix system

dig . a.root-servers.net NS > hints file

windows, as long as you do not setup the DNS as a root, it will/should have the root hints populated
matching nslookup -q=ns . a.root-servers.net
0
 
LVL 2

Assisted Solution

by:Michael Rojek
Michael Rojek earned 125 total points
ID: 40603528
There's 11 IP tools, including a DNS auditor in the NetCrunch Tools freeware app to help you do some digging.
0

Featured Post

Manage your data center from practically anywhere

The KN8164V features HD resolution of 1920 x 1200, FIPS 140-2 with level 1 security standards and virtual media transmissions at twice the speed. Built for reliability, the KN series provides local console and remote over IP access, ensuring 24/7 availability to all servers.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

SSL is a very common protocol used these days when browsing the web.  The purpose is to provide security to communication, but how does it do it?  There are several pieces at work that have to be setup before SSL will even work and it requires both …
BIND is the most widely used Name Server. A Name Server is the one that translates a site name to it's IP address. There is a new bug in BIND (https://kb.isc.org/article/AA-01272), affecting all versions of BIND 9 from BIND 9.1.0 (inclusive) thro…
Viewers will learn how to properly install and use Secure Shell (SSH) to work on projects or homework remotely. Download Secure Shell: Follow basic installation instructions: Open Secure Shell and use "Quick Connect" to enter credentials includi…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

688 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