While testing a McAfee Enterprise Firewall running software 8.2.0, I had some problems with the creation of a NAT mapping. The firewall is configured as standalone firewall. All (NAT / access rule) configuration on the firewall is done using Access Control Rules. McAfee uses two types of NAT mapping:
I tried to publish an internal network component to the internet. I created a simple rule with the following parameters. These parameters are very straightforward and the configuration is similar to firewalls from different vendors:
|Application: SSH||Source Zone:
Public IP address
Private IP address
I tested the NAT mapping, but couldn’t connect to the internal component using the public IP address. The first step in troubleshooting is looking at the logging, but I couldn’t find any logging on the firewall. It looked like the traffic didn’t even reach the firewall.
We have a shared internet segment with multiple firewalls. So I started doubting the configuration of the different firewalls.
I looked at the configuration of the firewalls, but nobody was using the public IP address. With this in mind, I ruled out the ARP entry “problems” on the ISP router.
When using NAT on a public IP address, which isn’t the same as the interface IP address, the firewall has to proxy ARP the public IP address. So does the firewall proxy ARP for the public IP address?
I started looking at the rest of the configuration with emphasis on the network configuration. I noticed that I had the option to add an alias IP address to the external interface. This can be found under Network – Interfaces – external interface. I added the public IP address as alias.
You guessed it. The NAT mapping is working……