Asterisk showing Warning:

Hello,

When I am sending multiple calls sometimes asterisk show warning:

What does this mean ? How to resolve it ?

The combination of call-id, from tag to tag on a re-invite was rejected by the peer device.

I guess that it might happen if the re-invite collided with a BYE from the other side. Otherwise you need to fix the other device, or you could try disabling features (session timers, connected line presentation up, and session timers) that cause re-invites.

There is too little information to know if it there is anything really wrong, and if so whether it is resolvable. Normally you can only resolve it if you have made a configuration error, or you are using out of date software. You have provided neither details of your configuration nor the version of the software that you are using.

The most important information is what real life problem do you believe it is causing. Just removing confusing messages from the logs is not really a high priority.