This article shows how to find Paloalto firewall interface or Tunnel IP range based on PA-850 firewall.
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1. Login to the web interface, for example https://192.168.11.11
2. Go to Network > Virtual Routers
3. Click on default to open it.
4. Click on Static Routes. The Destination lists each interface or Tunnel IP range.
Please view this step by step video: