Sometimes we have to map a hostname to loopback address 127.0.0.1 by some reasons of development. This is a simple guide to show how to do that on MacOS 10.10 Yosemite.

Everythings starts with hosts file

Add the following line in /etc/hosts.

127.0.0.1 test.domain.com

If your local port goes with 80, this is all that you need to do. But mostly we start a develop web server with Non-80 port such as localhost:8080. So port forwarding comes.

Port Forwarding

From OS X 10.10, well-known ipfw has been removed completely. So we use pf which is the new recommanded way to do port forwarding.

First, add an anchor file /etc/pf.anchors/com.custom to contain the port forwarding rule.

rdr pass on lo0 inet proto tcp from any to 127.0.0.1 port 80 -> 127.0.0.1 port 8080

Then, add two lines to /etc/pf.conf to load your new rule. It is important where these lines go. Add this line right after rdr-anchor "com.apple/*":

rdr-anchor "custom"

Add this line directly after load anchor "com.apple" from `/etc/pf.anchors/com.apple":

load anchor "pow" from "/etc/pf.anchors/com.custom"

Next, reload the rules into pf by running

sudo pfctl -f /etc/pf.conf

Finally, enable pf by running

sudo pfctl -e

Now, input test.domain.com into your browser address bar, it will works.