Monitoring current traffic per VIP

Is your cacti server overloaded? The polling on cacti isn't very intelligent, and breaks easily under load. If your poll times go much above 30 seconds then you're heading into territory that will result in dropouts (Manifested usually as missing data).

 

 

BTW.. That looks like a lot of connections... I'd drop the idle connection timeout for udp/53 down to about 10 seconds... (Especially if they're not doing recursive queries, the first timeout for DNS is 5 seconds so even going down to 10 should ideally be too long to cause any problems).