we are upgrading to v7.2.5 on SPlunk Enterprise. Is SPlunk DB Connect v3.1.1 compatible with this version?
According to the documentation:
https://docs.splunk.com/Documentation/DBX/3.1.1/DeployDBX/Prerequisites
For 3.1.1:
Splunk Enterprise
This version of Splunk DB Connect is compatible with Splunk Platform versions 6.4.0 and later.
So yes, however, looking at the release notes there are numerous fixes, some of them specific to 7.0 and 7.2 which are addressed in later versions.
3.1.4 is the latest DBX, so you may want to consider testing and upgrading to that to avoid such issues