Onos GUI discovers some extra unknown hosts

1.I created 2 switch linear topology in mininet and connected to my onos controller.
2. I executed "Wipe-out please" command from onos cli
3. All switches,links and hosts got cleared
4. But onos GUI discovers some unknown hosts
5. In onos cli "hosts" command also we can see hosts without IP

onos> hosts
id=26:82:87:BE:F0:25/-1, mac=26:82:87:BE:F0:25, location=of:0000000000000003/2, vlan=-1, ip(s)=[]
id=36:A3:1B:35:A0:F7/-1, mac=36:A3:1B:35:A0:F7, location=of:0000000000000003/2, vlan=-1, ip(s)=[]
id=B2:99:92:9F:79:8A/-1, mac=B2:99:92:9F:79:8A, location=of:0000000000000001/2, vlan=-1, ip(s)=[]
id=DA:D3:01:C8:AE:DD/-1, mac=DA:D3:01:C8:AE:DD, location=of:0000000000000001/2, vlan=-1, ip(s)=[]

Additional scenario when we see unknown hosts in GUI:
Known Host to Unknown Host after OF swtich interface Down & UP:
If a Known host is connected to an OVS switch port and the same switch port/IF is brought down in the OVS, the hosts are deleted in ONOS as a result of port down message and when the port are up the Host is learned back. As the arp cache is not deleted in the host and the Host never sends an ARP message causing those host to be learned as UNKNOWN.