The document discusses configuring Ubuntu to use DNS caching to improve performance. It explains that DNS maps domain names to IP addresses. It then describes installing and configuring the Bind9 DNS server on Ubuntu to use the local loopback IP address of 127.0.0.1 for caching. Tests were run using the dig command to query domain names and IP addresses, showing query times improved after configuring DNS caching. The conclusion states that DNS caching can improve browsing speed and network performance by reducing latency and bottlenecks from repetitive DNS queries.

1. Chacón Chávez María Guadalupe
Ing. Desarrollo de Software
2014.Mar.11
UBUNTU DNS CACHING CONFIGURATION
First, inorder tounderstand the activity that we will be performing,we needtounderstand what
is exactly a DNS server and why are we changing it to a caching server.
Domain Name Service (DNS) is an Internet service that maps IP addresses and fully qualified
domain names (FQDN) to one another. In this way, DNS alleviates the need to remember IP
addresses. Computers that run DNS are called name servers. Ubuntu ships with BIND (Berkley
Internet Naming Daemon), the most widely deployed DNS server.
Installing Bind9
To install bind9 we run the command sudo apt-get install bind9 for whichit will asks us for root
administrator login and password.

2. Once installed it will display the unpackaging of the features, and It will display as replacement
of the files if Bind was previously installed in that machine

3. Once the bind process has been started,we access the configurationfiles which are located at
etc/bind9 for which we will also need to log in as root users.

4. Within the configurationfiles we will access sudo /etc/bind/named.conf.options to edit the
forwarders address withour ownloopback default gateway fromourISP.

5. To obtainthe loopback ipaddress we run the command ifconfig to display all the network
information,basedonthe example below we see that the loopback ipaddress forthis
computeris 127.0.0.1
`

6. We edit the default forwarders that we had,whichwere 8.8.8.8 andwe instead replace them
with 127.0.0.1 andsave the changes.

7. It is also very important to restart the bind daemon by using sudo /etc/init.d/bind9/restart

8. Afterthat we cantest the response time afterwe have changedourdns server to caching,by
using the command dig –x 127.0.0.1 andwe shouldget the Query time result which in this
case is 117msec.

9. Dig canalso work ondomains andprovide us with the query time as well, the following
example below,shows the query time forfacebook.cominits first try which resultedin
113msec.

10. In our third attempt we got for query time 47 msec indicatingthe fast response fromthe
server afterchangingit as caching.

11. CONCLUSION
The mainobjective of goingthroughthis process is simply to avoidDNS latency whichcancause
slow browsing andperformance when accessingthe internet, network congestion and also to
prevent bottle necks by shorteningthe query time and the TTL andRTT of the DNS server itself.
Also is especially beneficial for environments that have a large amount of resolver calls where
the majority of those calls are repetitive and the DNS information doesn’t change very
frequently. Resolving with caching resulted in a higher performance rate as previously
mentioned due to less processor use which also benefits the hardware’s life spam and usage.