Since Mavericks deprecated ipfw, we'll be using pf to allow port forwarding.

####1. anchor file Create an anchor file under /etc/pf.anchors/<file> with the following redirection rule:

rdr-anchor "forwarding"
rdr pass on lo0 inet proto tcp from any to 127.0.0.2 port 80 -> 127.0.0.1 port 40070

####2. Test the anchor file Parse and test your anchor file to make sure there are no errors:

sudo pfctl -vnf <file>

####3. Reference the anchor in pf.conf /etc/pf.conf is the main configuration file that pf loads at boot. We'll need to tell it to load the anchor we previously created:

anchor "forwarding"
load anchor "forwarding" from "/etc/pf.anchors/<file>"

####4. Load and enabling pf pf is not enabled by default in Mavericks, few ways to enable this:

• Manually load and enable from a pf.conf file via sudo pfctl -ef <file>

• Auto enable by creating a launch daemon via this doc to run pfctl -ef <file> on boot.

• Auto enable by adding an -e(enable) to the pfctl ProgramArgument in /System/Library/LaunchDaemons/com.apple.pfctl.plist like this:

  <key>ProgramArguments</key>
  <array>
  <string>pfctl</string>
  <string>-e</string>
  <string>-f</string>
  <string>/etc/pf.conf</string>
  </array>
  

####5. Forwarding across interfaces By default, pf does not forward between interfaces. Here's a snippet from man for pfctl with help from 2sidedfigure:

The packet filter does not itself forward packets between interfaces.  Forwarding can be enabled by setting the sysctl(8) variables net.inet.ip.forwarding and/or net.inet6.ip6.forwarding to 1.  Set them permanently in sysctl.conf(5).

We'll need to enable this by adding to /etc/sysctl.conf:

net.inet.ip.forwarding=1
net.inet6.ip6.forwarding=1