XIV. Miscellaneous Questions

The Domain Name System (or DNS) links host names to IP addresses. The way that DNS is handled on DrayTek routers varies depending on the firmware version and this article details how DNS is handled with different versions of firmware on DrayTek routers.
This article only applies to DrayTek routers and is not applicable other devices such as Access Points, Switches and Modems.

DNS Proxy with Advanced DNS Filtering

The router operates as a transparent DNS Proxy, which allows it to perform DNS Filtering, to apply either Web Content Filtering or URL Content Filtering to DNS queries. This allows the router to block access to HTTPS and other encrypted access methods; it does this by inspecting DNS queries that go through the router, including DNS queries made to external DNS servers. The router modifies DNS queries that the content filter blocks. Blocking access to content when it's blocked by the Web Content Filter or URL Content Filter.

DNS Filter to apply Content Filtering

The [CSM] > [DNS Filter] feature is linked to the Firewall's Filter Rules, this makes it possible to specified IPs from DNS filtering, schedule DNS Filtering or apply different DNS Filter profiles to different network segments.

When the router is used as the DNS server by client machines, the configuration of [CSM] > [DNS Filter] - DNS Filter Local Setting will apply instead.

Customising Local DNS

The [Application] > [LAN DNS] feature is able to specify custom DNS responses and supports wildcards - this allows the router to catch DNS queries to specified host names specified and will provide the IP address(es) specified in the LAN DNS profile.

For instance if a LAN DNS profile is configured with a hostname of "www.example.*", the router will modify the DNS response for any DNS queries that contain "www.example", such as www.example.co.uk and www.example.com.

To apply this custom DNS only to specific clients, there is an option to specify different DNS responses, depending on the IP range of the client making the DNS query, for instance a router with two VLANs can give a local IP address response to a client located on the same subnet as that server, while DNS queries made from the other VLAN will receive the public IP address.

Forwarding Specific DNS Queries to another DNS server

The LAN DNS feature also supports Conditional DNS Forwarding so that any DNS queries matching specified hostname suffix / prefix, such as *.local, could be set to go to a specified DNS server IP address such as a Windows domain server performing DNS for a local network. Conditional DNS forwarding will work regardless of the DNS server that the client machine is using.

DNS Cache

It also operates as a DNS Forwarder for client machines using the router as the DNS server. The router's DNS server has a DNS Cache, which can be checked and controlled from [Diagnostics] > [DNS Cache].