PIWIK in a Web Farm



I have set up PIWIK for our intranet hosted ASP.net web site which is in a web farm environment behind a load balancer.
PIWIK is hosted in an IIS server (Server XX) and the url of the same is specified in the hosted application. But it tracks only the first hit by any user i.e. subsequent visits by the same user that are directed to another server in the web farm (than the one served the first request)for load balancing are not recognised at all.
Am I missing any configuration setting here or should I setup PIWIK in all the web servers in the web farm please.

Thank you.