In 1988 RIP version 1, defined in RFC 1058, was released. The RFC even states that RIP v1 is based on Linux routed due to it being a “defacto standard”.

It uses classful addressing and uses broadcasting to send out updates to router neighbors. There is no subnet information included in the routing updates in classful routing, and it does not support CIDR addressing — subnets must all be the same size. Also, route summarization is not possible.

RIP v1 has no router authentication method, so it is vulnerable to attacks through packet sniffing, and spoofing.