RIP-1
RIP version 1 (RIP-1) is a classful (as opposed to classless) routing protocol. It supports the advertisement of protocol packets only in broadcast mode. Figure 1 shows the packet format. A RIP packet can carry a maximum of 25 entries. RIP is based on UDP, and a RIP-1 data packet cannot be longer than 512 bytes. The RIP-1 protocol packet does not carry any mask, so it can identify only the routes of the natural network segment such as Class A, Class B, and Class C. Therefore, RIP-1 does not support route aggregation or discontiguous subnet.
