I setup a external content type for a list that has ~ 6k rows (SalesPerson). I have setup the list threshold to be 50k in central admin so I can test this. I am not able to return any data when I try to create a external list based on this ECT. However, i created another ECT from a table that has few hundred rows (SalesRegions) and I am able to create External List from this ECT. I created the ECT using SharePoint Designer. Any idea what's is happening? I get "could not save changes" when I try to create an External List from SharePoint designer using SalesPerson ECT.
when surpassing the 2,000 items you have to set up a filter in your external content type in SP designer
More info : Define filters