I am using Comcast Internet service and my IP address assigned a short-term DHCP lease?

Some of the reasons that your device may obtain a short-term DHCP lease are as follows:

• The device is newly connected to the cable modem and this is the device's first lease.  This could be a device that you are connecting for the first time, a computer with a new network interface card (NIC), or the addition or removal of networking equipment.  A computer that has been turned off for an extended period of time may also be interpreted as newly connected by the DHCP server. 
• The device connected to the cable modem is not configured to DHCP.  DHCP configuration instructions for your router will need to be obtained from the router's manufacturer.  DHCP configuration instructions for all supported Windows Operating Systems can be found here. 
• Maintenance is being performed on the DHCP servers or elsewhere on the Comcast network. 
• The device connected to the cable modem is not functioning properly. 

Regardless of the length of the lease, a properly configured device will automatically renew the DHCP lease when the current lease expires.  This should not cause an interruption in service.