topic Secondary interface on same subnet creates overlapping subnet commit failure in General Topics

Secondary interface on same subnet creates overlapping subnet commit failure

SteveBallantyne — Wed, 13 Jul 2022 14:40:41 GMT

Hello all, I currently have a case open with support on this issue. But I am looking for some customer feedback.

We presently have *two routes* and two separate firewalls. 10.0.44.1/22 on my Palo Alto, and 10.0.45.1/22 on a legacy Cisco L3 router. The Cisco has been stripped down and only really serves as a default route to a end of life firewall. My goal is to lift 10.0.45.1/22 from the old Cisco router and place it on my Palo Alto. In so many words ... I want to create a "secondary" IP address on the same subnet so that 10.0.45.1 and 10.0.44.1 are used interchangeably.

If I try to add these two addresses on the same one interface, the Palo rejects the changes with overlapping subnets. Support had suggested using a separate physical interface. But that gave me the same error message.

EDIT: This is on a Palo Alto PA-3250

Most of the articles and posts I have looked at for this issue point to a customer VPN where two remote sites have the same subnet(s). That doesn't really apply to my case here, and the solutions don't really make sense for this scenario.

Any help or pointers would be appreciated!

Re: Secondary interface on same subnet creates overlapping subnet commit failure

OtakarKlier — Wed, 13 Jul 2022 19:23:18 GMT

Hello,

I dont think the PAN can do this? I would recommend repointing the devices to the correct gateway. If they are on DHCP, you should just be able to change the scope details and wait.

Regards,

Re: Secondary interface on same subnet creates overlapping subnet commit failure

SteveBallantyne — Thu, 14 Jul 2022 15:33:46 GMT

The problem with this is that I have a couple hundred devices with static IP addresses. Everything from printers, to interface boxes stuck to lab instruments, to managed switches, etc.