Archive

Posts Tagged ‘dns’

Setup of Static IP addresses on Ubuntu

December 21st, 2013 No comments

In these examples, I have used the OpenDNS servers, please change as appropriate.


sudo vi /etc/network/interfaces

Example contents:

auto l0 eth0
auto lo
iface lo inet loopback
iface eth0 inet static
address 10.1.10.xxx
netmask 255.255.255.0
network 10.1.10.0
broadcast 10.1.10.255
gateway 10.1.10.1
dns-nameservers 208.67.222.222 208.67.220.220
dns-search home


sudo vi /etc/resolv.conf

NOTE: I’m not 100% sure if this is required!
Add appropriate content, example:

nameserver 208.67.222.222
nameserver 208.67.220.220
search home

sudo restart networking
ifconfig
sudo ifdown eth0 && ifup eth0
sudo restart

REFERENCES:

Self-Elevating to make hosts file change in Windows

July 21st, 2013 No comments

Working on a Windows machine without elevated permissions can often be difficult for developers. One item that is often useful to change is the ‘hosts’ file. IN Windows 7 and 8 you can often ‘Self-Elevate’ to run a file, but it’s not always obvious how to edit a file in this manner. Some simple batch files can be helpful in this case as you can elevate them to do the actual work requiring permissions.

For example to make all requests to ‘example.com’ to be directed to your own machine…

@echo off
set hostspath=%windir%\System32\drivers\etc\hosts
echo 127.0.0.1 www.example.com >> %hostspath%
echo 127.0.0.1 example.com >> %hostspath%
exit

To replace the existing hosts file with one of your chosing from your desktop. (NOTE: you can change this file or path to anything).

copy "%UserProfile%\Desktop\hosts" "c:\Windows\System32\drivers\etc"

A standard ‘hosts’ file in Windows appears as such:

# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost

DNS Prefetching

March 24th, 2012 No comments

DNS is much like a phone book for the internet. For each domain name (or subdomain like ‘www’), there is an IP address that resembles a phone number. Getting the matching number for each domain can take some time and make your site appear slow, particularly on mobile connections. Fortunately, you can pre-request this information and speed up your site in most cases.

To enable a domains DNS lookup to be performed in advance of the request, you can add a single line to the <head> section of your page.

<link rel="dns-prefetch" href="//giantgeek.com" />

If you want to explicitly turn on (or off) this behavior, you can add one of the following, or their HTTP Header equivalents:

<meta http-equiv="x-dns-prefetch-control" content="on" />
<meta http-equiv="x-dns-prefetch-control" content="off" />

This is supported in all modern browsers:

  • Firefox 3.5+
  • Safari 5.0+
  • MSIE 9.0+

If should be noted that a similar method can be used to prefetch as page, but I will save that for a different article:
<link rel="prefetch" href="http://www.skotfred.com/" />

REFERENCES:

Web Proxy Autodiscovery Protocol (WPAD)

December 9th, 2011 No comments

If you take a close look at your logs you may occasionally see requests for a file named wpad.dat. This file is related to automatic proxy configuration in many browsers.

To provide this capability to your users and website,

  1. DNS:

    Default behavior is to traverse the domain in reverse, looking for one with a file named /wpad.dat

    Example (using my domain for example):
    wpad.www.giantgeek.com
    wpad.giantgeek.com
    wpad.com

  2. Then in httpd.conf, set the MIME type:
    AddType application/x-ns-proxy-autoconfig .pac
  3. Also in httpd.conf, add a redirect to the actual file you wish to use.
    Redirect permanent /wpad.dat http://www.giantgeek.com/proxy.pac
  4. In the new file, add the following default contents, modify if you use a proxy:

    /* 'proxy.pac' - This is the main function called by any browser
    NOTE: there is NO proxy!
    */
    function FindProxyForURL(url, host)
    {
    return “DIRECT”;
    } // End function FindProxyForUrl

REFERENCES:

Dotless IP Address

December 11th, 2009 No comments

This is a concept I had forgotten about until recently, it can often serve as a simple means of code obfuscation and is also sometimes referred to as “Decimal Address”.

Some background:

  • DNS is used to convert a URL/domain name into an IP address that is used to contact the remote machine.
    EXAMPLES:
    localhost = 127.0.0.7
    giantgeek.com = 99.138.127.198
  • IP addresses (as IPv4) are represented as groups of 4 hexadecimal or decimal octets.
  • Those numbers can be plugged into a simple formula to be represented as a single large integer.

As such, you can use the following as equivalents:

  • http://localhost
  • http://127.0.0.1
  • http://2130706433

REFERENCES:

Categories: WebStandards, Work Tags: , , , ,

Private Caching/Relay DNS Server

June 18th, 2007 No comments

Since I’ve run a few small websites (like this one) out of my home for years, I’ve found it useful to run a DNS server inside of my firewall. Not only does this make it easier to maintain the websites, but it allows me to lock down security and increase performance of many of my applications.

I run a the following services that use DNS:

  • Apache JAMES – mail server that does lookups to send email and filter inbound SPAM.
  • Analog – web server log analysis.
  • Apache HTTPD – web server, used to host websites, private domains used for internal purposes.

To make things more efficient, I currently have my DNS setup to forward all requests to OpenDNS, allowing for ‘adult’ website filters and analysis of DNS activity.

Some open-source/free DNS servers that I recommend:

Cheers!

Categories: Work Tags: , , , ,

OpenDNS

November 13th, 2006 No comments

I’ve used EveryDNS (free service) for years to host my DNS services.    Recently I found that they now offer public DNS service for lookups as OpenDNS.   While I still run my own private DNS server for caching and various private addresses.  I now do a simple forward lookup to their servers to gain the extra services they provide… notably Phishing  and typo protection.

Setup is very simple for most users, and even a non-technical person should have no problems following their installation instructions for a single computer/device or an entire network.
Happy networking!!!