Please see my network diagram for referance.
In all the systems IndiseA, InsideB, InsideC and InsideD are IP address assigned statically and also the DNS Server IP. (DNS Server located in Network B with Ip Address of 172.16.10.50). My Inside A,B,C and D systems are able to communicate DNS Server. But Some times the systems are if not using long time (around 5 hour) then the systems are loss the IP and trying to renew and not able to find.
Please let me know how the systems are loss the IP even statically assigned ? What is the permenent solution for short out this issue ?