topic No internet after changing ISP in General Topics

No internet after changing ISP

Dars_Em — Wed, 16 Apr 2025 01:34:43 GMT

PA-440, OS 10.1.14, Standalone

We just changed the ISP, the static IP in interface (WAN), updated the Virtual Router as well, NAT, PBF, Security Policy was checked, IKE Gateway.

But we couldn't browse the internet. The firewall management GUI is also accessible by the WAN interface Before (from the allowed host), but not now.

If i revert the settings and plug in again the old ISP, it works without problem.

What have I missed?

Re: No internet after changing ISP

OtakarKlier — Tue, 15 Apr 2025 18:46:36 GMT

Hello,

If everything works with the old config, then I would say the new ISP is not physically connected to the PAN. Are you using the same interface of the new and old ISP or a different one for each?

Regards,

Re: No internet after changing ISP

nohash4u — Tue, 15 Apr 2025 18:48:49 GMT

I would recommend double checking the configuration to ensure the correct IP addresses are added where they need to be. The troubleshooting tool is also useful (Device --> Troubleshooting), and taking packet captures on the untrust (WAN) interface can clarify what the firewall is actually seeing. I would need to see screenshots and/or output of the config to troubleshoot further.

Re: No internet after changing ISP

Dars_Em — Wed, 16 Apr 2025 00:58:20 GMT

I'm using the same interface but made sure all the settings of old ISP records were replaced by the new. I also tried using different interface but getting the same situation.

Re: No internet after changing ISP

jpomachagua — Wed, 16 Apr 2025 15:53:01 GMT

Hello @Dars_Em

Have you tried pinging the internet with the IP set on the interface? I'd also recommend clearing the ARP tables, just to be safe.

Regards

Re: No internet after changing ISP

Dars_Em — Wed, 16 Apr 2025 15:56:07 GMT

Hi, I tried both clearing the ARP and pinging host 8.8.8.8 from CLI but not responding.

Re: No internet after changing ISP

jpomachagua — Wed, 16 Apr 2025 15:59:38 GMT

Hello @Dars_Em

Here's what I recommend:

Configure the assigned IP on a laptop and connect it to the new ISP. If you can't get internet access, there might be an issue with the ISP.
Perform a traceroute with the firewall connected, and then with the laptop connected, to see where the packet is getting stuck.

Regards

Re: No internet after changing ISP

nohash4u — Wed, 16 Apr 2025 16:00:49 GMT

I still strongly recommend a packet capture being setup on your untrust / WAN interface. Food for thought - if you changed ISP to a different provider then you may need to account for something such as MTU on the WAN interface.