Using split DNS for websites hosted locally

The dev.freshports.org website is hosted on server in my basement. For you, that IP addresses resolves to a publicly available IP address. For me, that IP address resolves to an RFC 1918 address:

$ host dev.freshports.org
dev.freshports.org has address 10.55.0.24

Sometimes this is referred to as split dns, also known as split-horizon DNS, split-view DNS, split-brain DNS, or a fricking stupid thing to do).

How?

I have a DNS zone file at home for that single host. I have similar zone files for other hosts. This allows me to selectively override the public DNS. I do this for about 19 different hosts at home.

Why?

I could browse to the internal host (dev-nginx01.int.freshports.org) and everything works as expected. The problem arises when I copy/paste the URL for a blog post or to show someone on IRC how something is working at home. I want to use the same URL whether I am at home or away. I want the same URL to work for me and for those helping me work on FreshPorts.

I think most split-dns approaches would maintain two zone files for freshports.org, one public and one private. I didn’t want to do that. I didn’t want to make changes in two places for the same update.

Instead, I took the approach of creating a zone file for a single host.

In this post

In this post:

• FreeBSD 12.1
• bind 9.16.6
• pfSense 2.4.5-RELEASE-p1

The zone file

On my primary DNS server, in the named.conf file, I have this entry:

include "zones/zones.primary";

You don’t need to do it this way. I just like having one file which lists all the zones I include.

In that file, I have entries such as this:

zone "dev.freshports.org" {
  type master;
  file "zones/dev.freshports.org.db";
  allow-transfer { AllowZoneTransfer; };
  allow-query { any; };
  notify yes;
};

In turn, zones/dev.freshports.org.db contains this:

$ORIGIN .
$TTL 60	; 1 minute
dev.freshports.org		IN SOA	slocum.int.example.org. soa.example.com. (
				2017111100 ; serial
				10800      ; refresh (3 hours)
				1800       ; retry (30 minutes)
				2592000    ; expire (4 weeks 2 days)
				86400      ; minimum (1 day)
				)
			NS	slocum.int.example.org.
			NS	toiler.int.example.org.

$ORIGIN dev.freshports.org.

dev.freshports.org.	IN A 10.55.0.24

That should get you started down this dodgy path.