We have recently installed a Cisco SG300-52MP as a backbone router with DHCP server and voice VLAN. We have also discovered that when current DHCP lease is expired, the router issues a completely new DHCP address to the device, breaking active connections to it, if any. This also has a possibility for a Cisco IP phone to reset its network, potentially dropping it out of voice VLAN for an unknown reason, so I'd like to alter this behavior, and should a DHCP request would come hitting an expired lease, the router would re-allocate the same IP address to the device. How can I do this? I am primarily configuring the SG300 with browser, however I can perform CLI configuration if needed.
SG300 firmware is the latest, or at least one of the latest, 126.96.36.199.