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Cat9400 switch might experience physical interface configuration loss after an IOS-XE upgrade from the SmartLicensing-enabled release [17.03.01 and earlier] to SmartLicensing using Policy-enabled release [17.03.02 and later] if the configuration is not saved manually. All other configuration [global configuration, as well as logical interface configuration [Portchannel interfaces/Vlan SVI interfaces/Loopback interfaces/...], is retained. This problem is seen only when the switch was registered to CSSM/OnPrem Satellite prior to the upgrade, and the communication was successful. This issue can be identified by comparing the show running-config output where the physical interface configuration will be present to the show startup-config output where the physical interface configuration will be missing after the IOS-XE upgrade. If the switch ends up in this state, there is no immediate impact as the needed configuration is present in the running-config however should the switch reload due to a power outage or any other cause, the startup-config, which at this point is missing the physical interface configuration will be read and applied upon subsequent boot which will result in all the physical interfaces losing their original configuration.
Cat9400 switch IOS-XE upgrade from the SmartLicensing-enabled release [17.03.01 and earlier] to SmartLicensing using Policy-enabled release [17.03.02 and later] PKI certificates are regenerated upon the initial boot configuration is saved [due to PKI certificates being regenerated] before linecards come online and become operational
after the IOS-XE upgrade, compare the content of the show running-config output and the show startup-config output if the physical interface configuration is still present in the running-config but is already missing in the startup-config, then simply save the configuration by issuing the copy running-config startup-config command [in other words, this is the state just after the upgrade and before the subsequent reload] this action can also be automated via the following EEM script event manager applet STARTUP_CONFIG_FIXER authorization bypass event syslog pattern "Running configuration saved to NVRAM" maxrun 300 action 1 cli command "enable" action 2 wait 180 action 3 cli command "write memory" action 4 syslog msg "startup-config has been saved to prevent interface configuration loss" if the physical interface configuration is missing in both the running-config and the startup-config, then restore the configuration from backup [in other words, this is the state after the upgrade and after the subsequent reload]
This is a timing issue where SmartLicensing Agent will regenerate PKI certificates upon the initial boot, and as part of this operation, will also initiate saving the running-config into startup-config. If this action is started after the linecards have booted up and initialized, no issue will be seen. If this action is started before the linecards have booted up and initialized, the running-config at that time will not contain the physical interface configuration [which will only appear once the linecards come online] and this "partial" running-config will be written into the startup-config stored in the NVRAM. This problem will be exposed the next time the switch boots up and this startup-config is read and applied. This being a timing issue, it does not affect all IOS-XE upgrade cycles and if the SmartLicensing Agent/PKI-initiated config saved is delayed by any event upon the initial boot, this problem will not occur.