The Routing Information Protocol (RIP) is a distance-vector routing protocol. RIP version 1 (as classical RIP) uses unauthenticated packets to deliver routing information. RIP version 2 adds route tag, subnet mask and next hop -fields to earlier specification and provides also possibility to password authenticated routing service. RIPV2 packets can be cryptographically authenticated using keyed MD5 or SHA1 fingerprints over sent data. Cryptographic authentication improves security and greatly reduces the vulnerability of the RIPv2-based routing system from a passive attack. In nutshell, RIP is stable, widely supported and easy to configure protocol. It's implemented on top of the User Datagram Protocol as its transport protocol. It is assigned the reserved port number 520.