Using DNS proxy to manage the firewall using a domain name on internal subnets

05/07/2020 6 2588

DESCRIPTION:

For compliance purposes we usually get a signed certificate from a CA and use the domain name on the certificate to be bound with the WAN address of the firewall. We can then successfully access the firewall using the domain name mentioned on that certificate when outside the network.

But, while managing the firewall from LAN, you cannot use the same domain name as it points to an external address. This method helps you in achieving the same for any internal subnets.

RESOLUTION:

If you have an internal DNS server, you can easily create an A record for the domain name and associate that to the firewall’s IP address and manage the firewall using the domain name internally.

But if you do not have an internal DNS server, the only option is to modify the host file entry on every machine so that the domain name resolves to the firewall’s IP address. But, if you have a mobile device that needs to leave the network, it will create issues when you would like to access the Public domain over the Internet.

We can use DNS proxy and solve this problem very easily.

Let us assume that the domain we are using for the firewall is sonicwall.firewall.com and would like to use this when accessing the firewall on X0 subnet.

Procedure:

            1. Enable DNS proxy globally and on the internal interface you would like to use this on.

• To enable it globally Navigate to Manage | Network | DNS Proxy
  
• To enforce it on a specific interface, click on the configure button of the interface and check the ‘Enable DNS Proxy’ checkbox on the Advanced tab
  
  2. Set the DHCP appropriately so that it uses the SonicWall as the primary DNS server. You can by navigating to Manage | Network | DHCP Server. Select the appropriate Dynamic lease scope and make the changes on the DNS/WINS tab. You would need to do this change on your internal DHCP server if you are not using the SonicWall as the DHCP server for that specific interface.
  
  3. Add the following entry on the ‘Static DNS Proxy Cache Entries’ in the DNS proxy tab.
  
  4. You can now use the domain name sonicwall.firewall.com to login to the firewall when present on X0 subnet
  
  
  

  NOTE:You can also ping and SSH into the firewall using the same domain name. This makes the management a little easier as domains are always easier to remember than IP addresses.