RIP version 1 (RIP-1) is a classful routing protocol, which supports only the broadcast of protocol packets. Figure 1 shows the format of a RIP-1 packet. A RIP packet can carry a maximum of 25 routing entries. RIP is based on UDP, and a RIP-1 packet cannot be longer than 512 bytes. RIP-1 packets do not carry any mask information, and RIP-1 can identify only the routes to natural network segments, such as Class A, Class B, and Class C. Therefore, RIP-1 does not support route summarization or discontinuous subnets.