Lost 1 packet when Query F5 LTM

Hi.. We have setup a virtual Server to load balance 3 Windows DNS servers in LTM(implemented with route domain). We used iapp DNS template to configure from BigIP side, all seems ok. But when we try to resolve any address with nslookup we are getting DNS Request Timed out error. After the first time out, we are able connect to that VIP and able to resolve the host names.

C:\Users\user>nslookup

DNS request timeout

timeout was 2 seconds

Default Server: Unknown

Address: 10.10.10.10

> aaa.com

Server: UnKnown

Address: 10.10.10.10

Non-authoritative answer:

Name:  aaa.com

Address: 123.123.123.123

C:\Users\user>ping 10.10.10.10

Pinging 10.10.10.10 with 32 bytes of data:

Reply from 10.10.10.10 bytes=32 time=48ms TTL=51  

Reply from 10.10.10.10 bytes=32 time=48ms TTL=51

Reply from 10.10.10.10 bytes=32 time=48ms TTL=51

Reply from 10.10.10.10 bytes=32 time=48ms TTL=51

Ping statistics for 10.10.10.10:

  Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

  Minimum = 46ms, Maximum = 50ms, Average = 48ms