2 subnets on the same interface

Showing results for 
Show  only  | Search instead for 
Did you mean: 
Please sign in to see details of an important advisory in our Customer Advisories area.
Palo Alto Networks Approved
Palo Alto Networks Approved
Community Expert Verified
Community Expert Verified

2 subnets on the same interface

L1 Bithead

We current have 1 subnet linked to an layer 3 interface which is supplied by our isp. We have run out of ip addresses and our isp want to present another subnet but on a completely different range. (too many services to move to a new range)

Is it just a case of adding an ip address from the new subnet to the current interface so there will be 2 gateways ?



Cyber Elite
Cyber Elite

Hi @Patrick_Jessett ,


You do not need to add another subnet to your interface.  As long as the ISP has a route for the new subnet to your existing IP address, it will work fine.  Notice in the 3rd paragraph of this article -> https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClSDCA0 that for "NAT configuration, the additional IP addresses do not necessarily need to be configured on the interface".  Configure NAT for IP addresses in the new subnet, and the NGFW will translate them.


This practice of NATing a different subnet than on the interface is quite common and works well for exactly this scenario.  All firewalls do it, and you do not need to burn an IP address on the interface.





Help the community: Like helpful comments and mark solutions.
  • 1 replies
Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the LIVEcommunity as a whole!

The LIVEcommunity thanks you for your participation!