08-03-2026 09:24 PM - edited 08-03-2026 09:26 PM
Hello,
We have a Palo Alto PA-445 firewall connected to a pair of Cisco IE9320 core switches configured as a stack, with one link connected to each switch. The links are configured in a Port-Channel on the Cisco side and as an AE (Aggregate Ethernet) interface on the Palo Alto firewall. Additionally, the MAC persistency timer is configured to 0 on the Cisco stack to avoid MAC address changes during a switch reboot or failover.
However, when Core Switch 1 is powered off, the AE interface on the Palo Alto briefly flaps can be seen on cisco switch logs and connectivity is interrupted for a short period before traffic resumes through the remaining active link connected to Core Switch 2. We expected traffic to continue seamlessly through the surviving link without any noticeable disruption. We would like to understand the reason for this temporary outage and identify any configuration changes that may improve failover behavior.
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