Disclaimer

Known affected versions were inferred from fixed-version data and were not explicitly confirmed by the vendor: 12.1.3-h3

The earliest recollection of this bug is traced back to PAN-OS 12.1.4 - October 28, 2026. This bug is fixed in PAN-OS versions 12.1.4, 12.1.5. Fixed an issue where the firewall did not forward STP frames on Layer 2 VLAN interfaces, which prevented the construction of loop-free topologies with connected switches. For more information: https://docs.paloaltonetworks.com/ngfw/release-notes/12-1/pan-os-12-1-4-known-and-addressed-issues/pan-os-12-1-4-addressed-issues https://docs.paloaltonetworks.com/ngfw/release-notes/12-1/pan-os-12-1-5-known-and-addressed-issues/pan-os-12-1-5-addressed-issues