Configure PAT on firewall

Port Address Translation (PAT), also known as NAT overload, is a technique used to allow multiple devices on a local network to be mapped to a single public IP address (or a few addresses) while maintaining unique private IP addresses for each device. PAT is commonly used in routers and firewalls to facilitate multiple users accessing the internet through a single IP address.

Configuring PAT on a Firewall

Below are general steps for configuring PAT on a firewall. Note that the specific commands and configuration steps may vary depending on the actual firewall or router equipment you are using (Cisco, Juniper, Fortinet, etc.). Below is an example configuration using Cisco IOS:

Example: Cisco IOS Configuration for PAT

1. Access the Device:
   • Connect to your network device via console, SSH, or Telnet.
2. Enter Global Configuration Mode:enable configure terminal
3. Define the Inside and Outside Interfaces:
   You need to specify which interfaces are considered inside and outside.interface GigabitEthernet0/1 ip address 192.168.1.1 255.255.255.0 # Inside interface (Private) ip nat inside exit interface GigabitEthernet0/2 ip address dhcp # Outside interface (Public) ip nat outside exit
4. Define the Access Control List (ACL):
   Create an ACL to specify which IP addresses can be translated. You’ll generally want to allow all IPs from the internal range.access-list 1 permit 192.168.1.0 0.0.0.255 # Permit access from inside network
5. Configure the NAT Rule for PAT:
   Use the ip nat command to specify that you want to use NAT overload.ip nat inside source list 1 interface GigabitEthernet0/2 overload
6. Verify Configuration:
   You can check if PAT is configured properly and operating by using the following command:show ip nat translations show ip nat statistics
7. Save Configuration:
   Don’t forget to save your configuration after making changes.write memory

Notes:

• Always ensure that the security policies of your firewall are in place and allow the necessary traffic.
• This example uses IP addresses and interfaces that may differ on your specific equipment; be sure to adjust accordingly.
• PAT can be implemented similarly on other firewall platforms, but the syntax and commands will differ. Refer to the specific documentation for your device.

Example for Fortinet Firewall

If you are working with a Fortinet firewall, the command line configuration might look different:

1. Configure a One-to-One NAT:config firewall ippool edit "PAT-Pool" set startip 203.0.113.1 set endip 203.0.113.1 set type0 set comment "PAT Pool" next end.
3. Configure Firewall Policies:config firewall policy edit 1 set srcintf "internal" set dstintf "wan1" set srcaddr "all" set dstaddr "all" set action "accept" set nat enable set ippool "PAT-Pool" next end

Make sure to refer to your specific firewall documentation for precise commands and syntax.