|  | 8.6 | TCP/IP Fundamentals
| 8.6.1 | IP default gateways
IP Datagrams (packets) use default gateways as entry and exit points between subnets. The subnet mask for the default gateway and the network on which it resides must be the same. A default gateway is usually the computer or router that is connected to the local subnet and/or other networks, which can determine the best path for delivery to the destination network id. Packets that are too large for the gateway are fragmented with three additional pieces of information: a flag to indicate fragmentation has occurred, a fragment ID number; and a fragment offset number for reassembling the fragments into the original packet.