Check for errors when transferring to clickstream

tail -100 /var/log/dpi/fastdpi_alert.log|grep ERROR

If you have the following errors:

[ERROR   ][2015/07/20-20:26:48:307378][0x7fd749eac700] IPFIX : udp:10.0.251.7:1500 : 
  Error socket send to collector, rc=-1, errno=111 : Connection refused
[ERROR   ][2015/07/20-20:26:48:434784][0x7fd749eac700] IPFIX : udp:10.0.251.7:1500 : 
  Error socket send to collector ( repeat error 1 ), now ok.

1. check the cache server availability from the DPI side
2. check the ip address (if it has been changed) in the CACHE server configuration /var/cache/nginx/cs/.cs/cs.conf. If the IP address is changed you will need to stop and restart the CACHE server - More detail about the CACHE server configuration