What is the problem with Cisco SD-WAN when default-version is not set?

[yutashimamura2920]

I are currently operating our devuce with no default-version set, but there is no impact on traffic, and when we reboot the equipment, it starts up with the expected OS version.
Is there any problem when upgrading in the future?

I checked the Upgrade Guide and it seems to boot with the default version only when Software reset is performed.

[balaji.bandi]

check below guide ;

https://community.cisco.com/t5/networking-knowledge-base/sd-wan-device-upgrade/ta-p/4798101

[yutashimamura2920]

Thank you.
I understand the following:
If multiple OS versions (for example, 17.06.05 and 17.03.04) are on the device, and the default version is not set, it is unclear which OS the device will boot with.

**Set Default Version:**
Once the device boots up with the required image, we need to set the default version. This is important because if the device reloads for any reason, it will boot up with the default version.