How to make sure different virtual users using different ids in csv feeder?

Hi all,

I have a problem need your help.

In my scenario, I need to launch 100 virtual users to run against our web service, but thers is one limitation, we cannot use the same id for different virutal users.

So I use csv feeder with 1000 ids. When running this scenario with several virtual users, it works fine. But when I increase 100 virtual users, I found that there are some virtual users using the same id.

So my question is how can I avoid this?