Hello theire,
So normally once DRS in use with Migrations threshold "middle" > then VM's shouldn't balanced tooo much beetween the Hosts. so because if you have too much activities > then this is a Indicator for having to less Ressources. i have a Costumer with a Cluster. it's running since 6-7 years and from the statistic theire where only 181 migrations for 61 vm's. so not much at all. (So its not a Mainplan to split vmotion). it's nice too have once having the Ressources > but not a Must have.
So during Migration the Switches for sure getting Pressure on the Network Layer.
- Which Esxi + vCenter version do you have?
- Do you see something on the Network layers regarding active Logs + Ressource Usage,...
- How big is the Memory from you're test VM? same Problem with lower Memory Vm's ?
- do you have 1GB Full Duplex?
- How are you're vSwitches and Portgroups configured? Pnic's are all to same PSwitch like other Services? ( So normally Virtualization Service should be splitted from other Dedicated Services,.. not good to mix it > could cause Problems and serious Conditions).
- Do you have WLB in Vlan30? Could cause also massive Problems.
So because strange is > if you tell that outside the Vmware Machines are loosing connections > then first it sounds for me that a Network Physical Part is having Problems to Calc the Load and has to less Power ,.... to much stressed,.... (First Idea without knowing the Environment)
and duplicate IP's i hope is not the Problem at all 
.
Best regards
Max