How do I use Simple DNS Plus with my Cable/DSL Router (NAT Router)?

Computers and devices behind a NAT router all have private IP addresses (typically 192.168.x.x), which are translated into a shared public IP addresses by the router.

To run a server behind the router, incoming TCP/IP traffic must be "mapped" to the server on a private IP address based on port numbers.
NAT routers typically have a web interface with a section where you can configure "port mappings", "port forwarding", or something similar.

Simple DNS Plus (and other DNS servers) use port number 53 UDP and TCP.

So you need to map for incoming traffic to port 53 to be forwarded to the local IP address of the computer running Simple DNS Plus.
With some routers you must create two separate mappings - one for each protocol "UDP" and "TCP".
Other routers allow you to do this with a single port mapping for "BOTH".

This sample screen shot is from a Linksys router:

linksys1.png

NOTE: If you are running servers (any type) behind a NAT router, the DNS records for these servers must point to the public Internet IP address - not the private server IP address (192.168.x.x).

 Comments
Gravatar
7 Sep 2018 13:21 UTC
steve reader
how does this work with this set Up;

dns servers on a local network to resolve local addresses but also as caching dns for internet requests. all behind
nat fire wall ? help

73de Steve Reader
JH Software
11 Oct 2018 17:51 UTC
JH Software
if you will not be hosting any Internet domain names, then you don't need to open any ports in the NAT router.

Resolving Internet domain names and hosting local only domain names for local address, can be done with default settings.
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