SharePoint 2010 Crawl Service Consuming High Network Traffic

Hi...

We are experiencing some strange problem with our SharePoint 2010 server. When we try to start the Crawl service after few minutes it will fully consume our network result freezing all our internal services.  When we stop the service everything goes in normal state.  

We user SharePoint for Internal only and the data of Database on 160GB.

Kindly assist me in this strange behaviour 

2 SharePoint front-end  

2 Cluster SQL

Win2008 R2 6bbit with SP1

Thanks