Routing and NAT Order precedence

rmeddane — Wed, 20 Dec 2023 11:03:48 GMT

In palo alto firewall. What is done first routing or nat for :

Inbound traffic
Outbound traffic

In cisco routers, for outbound, Routing first then NAT, for inbound traffic, NAT first then Routing.

Re: Routing and NAT Order precedence

aleksandar.astardzhiev — Wed, 20 Dec 2023 14:04:16 GMT

With Palo Alto firewalls it is something similar, but bit more complex, because you have "NAT evaluation" and "Applying NAT" which are two separate actions.

As you can see NAT evalution, or NAT policy lookup is performed little after packet hits the firewall. FW will perform route lookup to identify egress zone (based on zone associated with egress interface from routing table). This egress zone will be used for NAT and security policy lookup.

After traffic is allowed by the firewall (match rule after security policy lookup), NAT will be applied using the NAT rule identified earlier.

The following discussion started by @TomYoung is probably explaining better - https://live.paloaltonetworks.com/t5/general-articles/nominated-discussion-precedence-of-routing-nat-policy/ta-p/526558

I would recommend to look at this link explaining traffic flow sequence over PAN FW. https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClVHCA0

topic Routing and NAT Order precedence in Next-Generation Firewall Discussions

Routing and NAT Order precedence

Re: Routing and NAT Order precedence