During an In-Service Software Upgrade (ISSU) on Cisco Nexus 9000 Series Switches, the LACP peer session is designed to remain up without any renegotiation or reset. This is because ISSU is a process that allows for software upgrades without disrupting the normal operation of the network. The default LACP timers and the ISSU process are designed to work together to maintain the session state even during the upgrade process. The Nexus upgrade process will force the chassis itself to upgrade disruptively if LACP fast is used, which is not the default setting. A disruptive upgrade means the chassis itself will fully reload, impacting all ports on the switch, not just the LACP fast ones. However, with the default aging timers, the LACP peer connection should not be affected1. References: * Cisco Nexus 9000 Series NX-OS Software Upgrade and Downgrade Guide2. * Cisco Community discussions on LACP and ISSU impact