Courseware:IT Advanced - 08 Using a custom DNS on your mobile phone

For the Reverse Proxy lesson, you will need to use a custom DNS on your mobile phone. Here is how.

Why use a custom DNS?

During the Reverse Proxy topic, we want to simulate a branch connected to the real internet. This includes

• the internet - which will be simulated by your own local area network
• the branch router - which is connected to the (simulated) internet by the IP411RIGHT
• the worldwide DNS system - which is simulated by the DNS service on your IP411RIGHT (so your mobile phone can find hq-dvl-ckl2.training.innovaphone.com)
• a customer's branch network- which is simulated by your trainee network

For this to work, the names of your services (e.g. hq-dvl-ckl2.training.innovaphone.com or apps-dvl-ckl2.training.innovaphone.com) must be resolved to the IP address of your PBX and App Platform. For the devices within your trainee network (e.g. your PC), this is already the case cause they use the DNS server on your IP411RIGHT.

However, to simulate remote access to your system, we need a device that is not located within your trainee network. So we use your mobile phone connected to your corporate network via WLAN. However, your mobile phone would normally not use the IP411RIGHT's DNS server but a standard DNS server (either your own company's DNS or the DNS of your provider or any publicly available DNS such as google's 8.8.8.8).

Therefore, we need to modify the settings on your mobile phone to also use a different DNS - your IP411RIGHT.

How to determine your DNS server address

The server address is the IP address of the ETH0 interface of your IP411RIGHT. You can see that on

• the  IP4 settings for ETH0 at IP4 / ETH0 and
• the  lesson checker page on your Devices page
  

But what if I have no mobile phone or no WLAN in my corporate network?

Don't worry, if you can't access your corporate network from your mobile phone via WLAN, you may also connect your laptop to your corporate LAN (using WLAN or Ethernet).

 Alternate scenario (using laptop as remote device)

However, keep mind that

• you need an extra switch port on the same LAN your IP411RIGHT is connected to (more precisely, where the ETH0 is connected to and what we refer to as corporate LAN)
• you may need to change your laptop's LAN connection from your trainee network to your corporate network and vice versa once in a while
• you should not connect your laptop to both your corporate network and your trainee network at the same time

Custom DNS on iOS

iOS on your Apple iPhone (or iPad) allows you to override the DNS settings received by DHCP.

Here is how:

• open the open the global Settings
• open the  Wi-Fi settings
• click on the  little i next to the currently active WLAN interface
• open the  DNS / Configure DNS settings
• change the  DNS mode to manual
• add the external IP address of your IP411RIGHT as new DNS server and remove the old one
• save all settings
  

Custom DNS on Android

Unfortunately, Android does not let you change your DNS settings easily. Most often, a so-called DNS changer App is used. The drawback however is, that these Apps come and go and also sometimes change their pricing policy.

We therefore rather recommend to use a little dirty trick: change your IP mode on the WiFi interface from DHCP to static.

WARNING: as said before, this is a dirty trick! It is absolutely essential that you revert the settings each evening! Otherwise you may create issues with duplicate IP addresses in your network.

Obtain your current IP settings

First you need to see how your mobile phone's WiFi interface is configured right now.

Here is how:

• get yourself a notepad to write down the current settings
• open your mobile phone's  Settings app
  
• tap on  Network & connection
• tap on  Wi-Fi
• tap on  the Wi-Fi network you are connected to
• now its the time to use your notepad
  take  note of IP Address, Gateway and Subnet mask

Set special options for for your training

To modify your network settings:

• go back to Network Info
  
• press long on  the Wi-Fi network you are connected to
  a context menu will be shown
  
• select  Modify network
• scroll down and open  Advanced options
• change
• IP settings from DHCP to Static
• IP address to the value you took note of before
• Gateway to the value you took note of before
• Network prefix length to the length that corresponds to the Subnet mask value you took note of before:
  
  

  Subnet mask	Network prefix length
  255.255.255.	24
  255.255.0.0	16
  255.240.0.0	12
  255.0.0.0	8
  other value	consult your network administrator

  
  
• DNS 1 to the external IP address of your IP411RIGHT
  

Reset your settings to defaults

It is absolutely essential that you revert the modified settings to the original values each evening!

To do so

• open your mobile phone's  Settings app
  
• tap on  Network & connection
• press long on  the Wi-Fi network you are connected to
  a context menu will be shown
  
• select  Modify network
• scroll down and open  Advanced options
• change
• IP settings from Static to DHCP

Verifying your DNS setting

To check your new DNS setting, open the browser on your mobile phone, type https://test.my.dns in the address bar and go to the site.

Your browser will most likely complain about an unsecure site due to a bad certificate (probably saying something like SSL_ERROR_BAD_CERT_DOMAIN). This is because your Moodle site's certificate is issued to *.innovaphone.com and this doesn't match test.my.dns. If this is the case, you could decide to continue at your own risk. However, you could just as well have a break at this point. The fact that you get this message already proves that your DNS is working as intended.

If you take the risk, you should see the Moodle home page and the address line should read http://test.my.dns/moodle2/?