Corresponding ipfw rules in MacOS for this Iptables rules

Question

I need to give Internet access to a VM under Vmware fusion 7 in Host-Only mode. I know how to do it in Linux, with the following IPtables rules:

sysctl -w net.ipv4.ip_forward=1
iptables -A FORWARD -o eth0 -i vboxnet0 -s 192.168.56.0/24 -m conntrack --ctstate NEW -j ACCEPT
iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A POSTROUTING -t nat -j MASQUERADE

Can this be done in MacOS Sierra?

klanomath · Accepted Answer · 2019-09-06T12:48:52.573

To enable NAT for a host-only network in VMware Fusion do the following:

Enable forwarding by adding a file /etc/sysctl.conf with the content:
```
net.inet.ip.forwarding=1
```
and reboot
Connect the Mac to the host-only network and make a note of the network/netmask of the host.only network:

Enter ifconfig to get the vmnet IP of the Mac

...
vmnet3: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        ether 00:50:56:c0:00:03 
        inet 192.168.9.1 netmask 0xffffff00 broadcast 192.168.9.255

In the IP setting of the guest VM enter an IP/netmask according to the host-only network settings (with the example above that's in the range 192.168.9.2-254/255.255.255.0), a gateway (the vmnet3 IP of the hosting Mac from step 3 - here: 192.168.9.1) and a DNS server.
Open the pf.conf file with:
```
sudo nano /etc/pf.conf
```
and add the lines:
```
nat on {en0, en1} proto {tcp, udp, icmp} from 192.168.9.0/24 to any -> {en0, en1}
pass from {lo0, 192.168.9.0/24} to any keep state
```
after the line rdr-anchor "com.apple/*".

Depending on your Mac and your network configuration only one interface is sufficient (either en0 or en1). Also use the proper network/netmask (your vmnet config instead of 192.168.9.0/24)!.

Save the file and exit nano.
Check your pf.conf with:
```
sudo pfctl -vnf /etc/pf.conf
```
If no error occurs enable pf with:
```
sudo pfctl -ef /etc/pf.conf
```

After a reboot you have to relaunch pf because it's not started automatically while booting. To launch pf while booting check step 4 in this answer: What is the modern way to do port-forwarding on El Capitan? (forward port 80 to 8080)

@klanomath, thanks for an excellent answer. Why do you NAT on {en0,en1}, when ifconfig reports the interface as vmnet3? Furthermore, please correct "the IP of the Mac from step 2" to "the IP of the Mac from step 3". — Shuzheng, Sep 05 '19 at 18:56
@Shuzheng You have to enable NAT on a "public" interface (which usually is either en0 or en1) of a NAT gateway. Vmnet3 is a "private" interface by definition and has no connection to the world. — klanomath, Sep 06 '19 at 13:15
@klanomath, indeed, but doesn't the packages pass the vmnet3 interface (and not en0), when going from the host-only network to the Internet? The guest VM sends it's packets to the vmnet3 interface of the host. — Shuzheng, Sep 06 '19 at 13:53

Corresponding ipfw rules in MacOS for this Iptables rules

1 Answers1