Source NAT
Source NAT is typically used by internal users to access
the Internet; the source address is translated and thereby kept
private. There are three types of source NAT:
- Static IP—Allows the 1-to-1, static translation of a source IP address, but leaves the source port unchanged. A common scenario for a static IP translation is an internal server that must be available to the Internet.
- Dynamic IP—Allows the one-to-one, dynamic translation of a source IP address only (no port number) to the next available address in the NAT address pool. The size of the NAT pool should be equal to the number of internal hosts that require address translations. By default, if the source address pool is larger than the NAT address pool and eventually all of the NAT addresses are allocated, new connections that need address translation are dropped. To override this default behavior, useAdvanced (Dynamic IP/Port Fallback)to enable use of DIPP addresses when necessary. In either event, as sessions terminate and the addresses in the pool become available, they can be allocated to translate new connections.Dynamic IP NAT supports the option for you to Reserve Dynamic IP NAT Addresses.
- Dynamic IP and Port (DIPP)—Allows multiple hosts to have their source IP addresses translated to the same public IP address with different port numbers. The dynamic translation is to the next available address in the NAT address pool, which you configure as aTranslated Addresspool be to an IP address, range of addresses, a subnet, or a combination of these.As an alternative to using the next address in the NAT address pool, DIPP allows you to specify the address of theInterfaceitself. The advantage of specifying the interface in the NAT rule is that the NAT rule will be automatically updated to use any address subsequently acquired by the interface. DIPP is sometimes referred to as interface-based NAT or network address port translation (NAPT).DIPP has a default NAT oversubscription rate, which is the number of times that the same translated IP address and port pair can be used concurrently. For more information, see Dynamic IP and Port NAT Oversubscription and Modify the Oversubscription Rate for DIPP NAT.(Affects only PA-7000 Series firewalls that do not use second-generation PA-7050-SMC-B or PA-7080-SMC-B Switch Management Cards) When you use Point-to-Point Tunnel Protocol (PPTP) with DIPP NAT, the firewall is limited to using a translated IP address-and-port pair for only one connection; the firewall does not support DIPP NAT. The workaround is to upgrade the PA-7000 Series firewall to a second-generation SMC-B card.Beginning with PAN-OS 10.1.6, persistent NAT for DIPP is available on VM-Series firewalls and single-dataplane firewalls. Beginning with PAN-OS 10.1.7, it is available on all firewalls.VoIP, video, cloud-based video conferencing, audio conferencing, and other applications often use DIPP and may require the Session Traversal Utilities for NAT (STUN) protocol. DIPP NAT uses symmetric NAT, which may have compatibility issues with applications that use STUN. To alleviate these issues, persistent NAT for DIPP provides additional support for connectivity with such applications.When persistent NAT for DIPP is enabled, the binding of a private source IP address/port pair to a specific public (translated) source IP address/port pair persists for subsequent sessions that arrive having that same original source IP address/port pair. The following example shows three sessions:
In this example, original source IP address/port 10.1.1.5:2966 is bound to the translated source IP address/port 192.168.1.6:1077 in Session 1. That binding is persistent in Session 2 and Session 3, which have the same original source IP address/port, but different destination addresses. The persistence of the binding ends after all of the sessions for that source IP address/port pair have ended.In Session 1 of the example, the Destination port is 3478, the default STUN port.When persistent NAT for DIPP is enabled, it applies to all NAT and NAT64 rules subsequently configured; it is a global setting. Management plane or dataplane logs will indicateNAT DIPP/STUN support has been enabled.The persistent NAT for DIPP setting (enabled or disabled) survives across firewall reboots.
